FIELD OF THE INVENTION
[0001] The present disclosure relates to a wireless communication method and a wireless
communication apparatus, and more particularly to a wireless communication method
and a wireless communication apparatus for a massive multiple input multiple output
communication system.
BACKGROUND
[0002] Recently, Massive Multi-Input Multi-Output (MIMO) technique and Millimeter Wave technique
have been considered as a part of critical 5G technology in the future, and have attracted
wide attentions from the academia and industry. The Millimeter Wave band has a large
amount of available spectrum resources to meet growing traffic demands of mobile communications.
In addition, due to short wavelength of the millimeter wave, according to the related
antenna theory, sizes of antennas for a millimeter wave system are small, so that
hundreds or even thousands of antennas can be arranged in a small space, which is
more advantageous for usage of a large-scale antenna technology in a real system.
In addition, a beamforming technology provided by large-scale antennas can effectively
compensate for shortcoming of millimeter-wave channel paths attenuating excessively,
which makes it possible to apply the millimeter-wave technology to mobile communications.
[0003] Full Dimension Multiple Output Multiple Output (Full Dimension MIMO, FD-MIMO) antenna
technology, also be referred to as Uniform Planar Array antenna technology, is also
one of hot spots attracting attentions from the industry. Compared with traditional
linear antenna arrays, FD-MIMO can deploy more antennas in a limited space, thereby
improving performances of spatial diversity and multiplexing. In the existing 3GPP
standardization work, a two-dimensional planar antenna array (or be referred as full-dimensional
MIMO, FD-MIMO) has become one of core technologies of a future 5G standard. In a Massive
MIMO scenario, especially in a FD-MIMO scenario, how to reduce hardware complexity
while ensuring antenna transmission performance has become a research focus of the
industry.
DISCLOSURE OF THE INVENTION
[0004] The inventors of the present disclosure have found that when a first communication
apparatus (e.g., a transmitter end, such as a base station end) in a wireless communication
system is equipped with large-scale antennas, especially two-dimensional planar array
antennas, an existing phase-shifting network architecture used for beamforming is
difficult to ensure optimization of both antenna transmission performance and hardware
complexity. Further, when there are multiple user equipments (second communication
apparatuses, for example, receivers), there are often a plurality of radio frequency
chains, the phase-shifting network architecture between the plurality of radio frequency
chains and two-dimensional planar array antennas will be more complicated.
[0005] Accordingly, it is an object of the present disclosure to provide an improved technique
for beamforming, particularly a solution for a millimeter wave communication system
equipped with planar array antennas.
[0006] In view of this, the present application proposes an improved beamforming architecture,
whose basic idea is for the planar array antenna used by each radio frequency chain,
to design a two-layer phase shifting network for performing phase modulation and control
for each layer respectively. In one implementation, the phase shifting network is
split into a horizontal phase-shifting layer and a vertical phase-shifting layer.
The configuration of a two-layer phase-shifting network enables independent selection
of the precision of phase shifters in each layer for phase modulation and control.
[0007] The present application also proposes an improved beamforming architecture, whose
basic idea is that planar array antennas may comprise a plurality of sub-arrays, each
user or radio frequency chain finally performs communication using a beamforming result
obtained by combining at least one of the plurality of sub-arrays. In one implementation,
the planar array antennas include a plurality of sub-arrays, and for each radio frequency
chain, a first beamforming training is performed by a corresponding sub-array, and
a second beamforming training is performed by at least one sub-array of the plurality
of sub-arrays other than the corresponding sub-array, so that final configuration
parameters for data communication are obtained from configuration parameters separately
obtained by the first and second beamforming trainings.
[0008] The present application also proposes an improved beamforming architecture, whose
basic idea is that planar array antennas may comprise a plurality of sub-arrays, each
of which is connected to at least one antenna sub-array via a two-layer phase-shifting
network, thereby using a beamforming result combined by at least one of a number of
sub-arrays for communcation. For each subarray, a number of radio frequency chains
are connected to the same vertical or horizontal phase shifter.
[0009] According to an aspect of the present disclosure, there is provided an electronic
equipment for a first communication apparatus of a wireless communication system,
comprising: a number of antenna sub-arrays, each sub-array being a planar antenna
array, each column or row in the sub-array corresponding to one input terminal; a
plurality of sets of first direction phase shifters, wherein the first direction phase
shifters in each set are disposed between input terminals of the corresponding sub-arrays
and a radio frequency chain, wherein each set of the plurality of sets of first direction
phase shifters is configured to adjust a first direction angle of an antenna beam
for transmitting a corresponding radio frequency chain signal in a first direction
in accordance with a first control signal.
[0010] According to another aspect of the present disclosure, there is provided a method
for a first communication apparatus of a wireless communication system, the first
communication apparatus comprising: a number of antenna sub-arrays, each sub-array
being a planar antenna array, each column or row in the sub-array corresponding to
one input terminal; a plurality of sets of first direction phase shifters, wherein
the first direction phase shifters in each set are disposed between input terminals
of the corresponding sub-arrays and a radio frequency chain, the method comprises
adjusting a first direction angle of an antenna beam for transmitting a corresponding
radio frequency chain signal in a first direction in accordance with a first control
signal.
[0011] According to another aspect of the present disclosure, there is provided a method
for a first communication apparatus of a wireless communication system, wherein the
first communication apparatus is equipped with a number of atenna sub-arrays and a
number of radio frequency chains, the method includes for each of at least one radio
frequency chain of the number of radio frequency chains, performing a first communication
with a second communication apparatus in the wireless communication system via a first
one of the number of antenna sub-arrays corresponding to the radio frequency chain,
so that a first communication configuration parameter is determined; and performing
a second communication with the second communication apparatus via at least one of
remaining sub-arrays of the number of sub-arrays other than the corresponding first
sub-array, so that a second communication configuration parameter is determined, wherein
a communication configuration parameter for the radio frequency chain is determined
based on the first communication configuration parameter and the second communication
configuration parameter.
[0012] According to another aspect of the present disclosure, there is provided an electronic
equipment for a first communication apparatus of a wireless communication system,
wherein the first communication apparatus includes a number of atenna sub-arrays and
a number of radio frequency chains, the electronic equipment includes a processing
circuitry configured to: for each of at least one radio frequency chain of the number
of radio frequency chains, perform a first communication with a second communication
apparatus in the wireless communication system via a first one of the number of antenna
sub-arrays corresponding to the radio frequency chain, so that a first communication
configuration parameter is determined; and perform a second communication with the
second communication apparatus via at least one of remaining sub-arrays of the number
of sub-arrays other than the corresponding first sub-array, so that a second communication
configuration parameter is determined, wherein a communication configuration parameter
for the radio frequency chain is determined based on the first communication configuration
parameter and the second communication configuration parameter.
[0013] According to another aspect of the present disclosure, there is provided an electronic
equipment for a second communication apparatus of a wireless communication system,
the electronic equipment includes a processing circuitry configured to: for a corresponding
radio frequency chain of a first communication apparatus in the wireless communication
system, acquire a channel state information in a first communication performed by
the first communication apparatus with respect to the second communication apparatus
via a first one of a plurality of antenna sub-arrays of the first communication apparatus
corresponding to the radio frequency chain, so that a first communication configuration
parameter is determined is based on the channel state information; and acquire a channel
state information in a second communication performed by the first communication apparatus
with respect to the second communication apparatus via at least one of remaining antenna
sub-arrays of the plurality of antenna sub-arrays of the first communication apparatus
other than the corresponding first antenna sub-array, so that a second communication
configuration parameter is determined is based on the channel state information, wherein
a communication configuration parameter for the radio frequency chain is determined
based on the first communication configuration parameter and the second communication
configuration parameter
[0014] According to another aspect of the present disclosure, there is provided a method
for a second communication apparatus of a wireless communication system, comprising:
for a corresponding radio frequency chain of a first communication apparatus in the
wireless communication system, acquiring a channel state information in a first communication
performed by the first communication apparatus with respect to the second communication
apparatus via a first one of a plurality of antenna sub-arrays of the first communication
apparatus corresponding to the radio frequency chain, so that a first communication
configuration parameter is determined is based on the channel state information; and
acquiring a channel state information in a second communication performed by the first
communication apparatus with respect to the second communication apparatus via at
least one of remaining antenna sub-arrays of the plurality of antenna sub-arrays of
the first communication apparatus other than the corresponding first antenna sub-array,
so that a second communication configuration parameter is determined is based on the
channel state information, wherein a communication configuration parameter for the
radio frequency chain is determined based on the first communication configuration
parameter and the second communication configuration parameter.
[0015] According to another aspect of the present disclosure, there is provided an electronic
equipment for a first communication apparatus of a wireless communication system,
comprising: a number of antenna sub-arrays, each sub-array comprising a plurality
of antennas, each antenna being connected to at least one phase shifter; and a plurality
of additional phase shifters, each additional phase shifter being disposed between
one sub-array and one radio frequency chain, such that one radio frequency chain is
connected to a plurality of antenna sub-arrays through a plurality of additional phase
shifters, respectively.
[0016] According to an embodiment of the present disclosure, antenna sub-arrays for the
first communication apparatus are capable of implementing RF-chain specific horizontal
or vertical beam adjustment.
[0017] According to an embodiment of the present disclosure, a radio frequency chain is
capable of utilizing spatial diversities of at least some of all sub-arrays in wireless
communication to increase a beamforming gain.
[0018] According to an embodiment of the present application, hardware complexity can also
be significantly reduced with less performance penalty.
[0019] Other features and advantages of the present invention will become apparent from
the following detailed description of exemplary embodiments of the present disclosure
with reference to the accompanying drawings.
DESCRIPTION OF THE DRAWINGS
[0020] The accompanying drawings, which are incorporated in and constitute a part of this
specification, illustrate embodiments of the present disclosure and, together with
the description, serve to explain the principles of the present disclosure.
[0021] The present disclosure will be more clearly understood from the following detailed
description with reference to the accompanying drawings, in which:
FIG. 1 is a diagram showing the structure of a prior art base station (BS).
FIG. 2 is a diagram showing a user equipment (UE) equipped with a single antenna.
FIG. 3 is a diagram showing a user equipment equipped with a plurality of antennas.
FIGs. 4a and 4b are diagrams showing configurations of a base station and a user equipment
in a single-user system, respectively.
FIGs. 5a and 5b are diagrams showing configurations of a base station and a user equipment
in an analog-digital hybrid precoding architecture, respectively.
FIGs. 6a and 6b show schematic diagrams of a full-connection phase shifting network
and a sub-connection phase shifting network, respectively.
FIG. 7a shows a schematic diagram of an electronic equipment for a communication apparatus
in a wireless communication system, in accordance with one embodiment of the present
invention.
FIG. 7b shows a schematic diagram of an electronic equipment for another communication
apparatus in a wireless communication system, in accordance with one embodiment of
the present invention.
FIG. 8 shows a flow chart of beamforming training in a base station by using the electronic
equipment of FIG. 7a and/or FIG. 7b, in accordance with one embodiment of the present
invention.
FIG. 9a shows a schematic diagram of a hybrid connection architecture based on a number
of sub-arrays for an examplary base station employing the communication configuration
process depicted in FIG. 8.
FIG. 9b shows a schematic diagram of a phase-shifting network for each antenna sub-array
in the examplary base station shown in FIG. 9a.
FIG. 9c shows a schematic diagram of another configuration of a phase shifting network
for each antenna sub-array in the example base station shown in FIG. 9a.
FIGs. 10a and 10b illustrate an examplary precoding process for an examplary base
station based on a multi-subarray hybrid connection architecture.
FIG. 11a shows a schematic diagram in which a number of subarrays are in the same
plane.
FIG. 11b shows a schematic diagram in which a number of sub-arrays are not in the
same plane.
FIG. 12a shows a schematic diagram of a two-layer phase shifting network design employing
a vertical priority structure.
FIG. 12b shows a schematic diagram of a two-layer phase shift network design using
a horizontal priority structure.
FIG. 13 shows a performance comparison of the proposed vertical priority structure
to a legacy architecture.
FIG. 14 illustrates an examplary hybrid connection architecture for a multi-user wireless
communication system being extended from the two-layer phase shifting network of the
vertical priority structure of FIG. 12a.
FIGs. 15a and 15b show schematic diagrams of a hybrid connection hybrid precoding
architecture in a vertical priority structure and a two-layer phase shifting network
for each subarray therein, respectively.
FIG. 16 shows an exemplary precoding design flow.
FIG. 17 shows an examplary implementation for determining a beamforming vector and
an additional phase and power allocation factor after combining.
FIG. 18 illustrates an examplary implementation for determination of a combined beamforming
vector and an additional phase and power allocation factor when employing a simplified
beamforming training method.
FIG. 19 shows performance simulation results of the hybrid connection architecture.
FIG. 20 shows an example of a hardware configuration of an electronic equipment according
to the present disclosure.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] Various exemplary embodiments of the present disclosure will now be described in
detail with reference to the accompanying drawings. Notice that, unless otherwise
specified, relative arrangement, numerical expressions and numerical values of components
and steps set forth in these examples do not limit the scope of the invention.
[0023] Meanwhile, it should be understood that, for ease of description, dimensions of various
parts shown in the drawings are not drawn in actual proportions.
[0024] The following description of at least one exemplary embodiment is in fact merely
illustrative and is in no way intended to limit the invention, its application or
use.
[0025] Techniques, methods, and apparatus known to those of ordinary skill in the relevant
art may not be discussed in detail, but where appropriate, these techniques, methods,
and apparatuses should be considered as part of the specification.
[0026] In all the examples shown and discussed herein, any specific value should be construed
as merely illustrative and not as a limitation. Thus, other examples of exemplary
embodiments may have different values.
[0027] Note that, similar reference numerals and letters denote similar terms in the accompanying
drawings, and therefore, once an item is defined in a drawing, there is no need for
further discussion in the accompanying drawings.
Digital Precoding - Digital Baseband processing
[0028] In a conventional wireless communication system, usually, at a transmitting end (for
example, a base station) and a receiving end (for example, a user equipment), each
antenna is connected to one radio frequency (RF) chain for transmission and reception.
Generally speaking, in operation, at the transmitting end, a data stream to be transmitted
is first subjected to baseband processing, and then converted into a radio frequency
signal via a radio frequency chain so as to be transmitted via a corresponding antenna,
and a corresponding radio frequency chain at the receiving end receives the radio
frequency signal and processes it into a baseband signal, and then the baseband signal
is further subject to baseband processing to obtain a desired data stream.
[0029] Generally, in the baseband data processing, in order to facilitate a plurality of
data streams multiplexing the same transmission resource and being transmited via
a radio frequency chain and a corresponding antenna, a digital precoding architecture
is mainly used, in which respective magnitudes of signals transmitted over respective
radio frequency chains each can be adjusted, to reduce interference between multiple
channels of data signals carried on the same transmission resource. Such processing
before data being transmitted via the radio frequency chain and antenna may be referred
to as data baseband digital processing at the transmitting end.
[0030] For example, FIG. 1 schematically illustrates a conceptual structure of a prior art
base station. As shown in FIG. 1, in a digital precoding architecture, the base station
is equipped with M antennas (M is an integer and M ≥ 1), and each antenna is arranged
with a corresponding radio frequency chain. Under control of the controller, the digital
precoder obtains a K-way data stream (K is an integer and K ≥ 1), and digitally pre-codes
the K-way data stream (for example, causing the K-way data stream to pass through
a digital precoding matrix B of a size of M×K). The encoded data is transmitted to
one or more user equipments via the radio frequency chains and the antennas.
[0031] Correspondingly, the user equipment can have a variety of configurations, so as to
perform corresponding baseband digital processing after receiving the encoded data
over the radio frequency chains to obtain the desired data stream.
[0032] FIG. 2 shows a user equipment equipped with a single antenna. As shown in Figure
2, the UE is equipped with a single antenna and a corresponding single RF chain. Since
the user equipment has only one antenna, it can only receive a single data stream.
That is to say, in the K-way data stream sent from the M antennas of the base station,
only one data stream can be received by the UE by means of a corresponding digital
processing.
[0033] FIG. 3 shows a user equipment equipped with multiple antennas. As shown in FIG. 3,
the UE is equipped with N antennas (N is an integer and N>1). Each antenna transmits
the received data to the digital precoder via a corresponding radio frequency chain.
Under control of the controller, the digital precoder performs digital precoding on
the received data by using, for example, a digital precoding matrix W of a size Ku
× N (Ku is an integer and Ku ≥ 1), thereby obtaining a single path data (when Ku =
1) or multiplexed data (when Ku>1).
[0034] For the digital precoding matrix used in the digital precoder, there usually exists
two design ways: a codebook-based way and a non-codebook based way. In a codebook-based
design, the digital precoding matrix must be selected from preset codebooks. In a
non-codebook based design, there is no such constraint. The base station and the UE
can design the precoding matrixes according to Channel State Information (CSI).
[0035] The above digital precoding process can be considered as belonging to the baseband
digital processing portion in the wireless communication.
Analog Beamforming - Radio Frequency Portion
[0036] Further, in a wireless communication system, especially a high frequency, such as
millimeter wave, communication system, every RF chain can be connected to a plurality
of phase shifters and antennas so that directional beams can be formed by using as
few as one RF chain, thereby implementing an analog beamforming scheme. Analog beamforming
training refers to a process of optimizing radio frequency configuration information
of a base station and a user equipment (for example, configuration values of phase
shifters related to the base station and the user equipment, also referred to as weight
vectors for the phase shifters), and mainly functions as improving a reception signal
to noise ratio for a user equipment. Taking the downlink as an example, a base station
forms directional transmission beams by configuring values of a plurality of phase
shifters connected to a plurality of antennas thereof, and the user equipment forms
directional reception beams by configuring values of a plurality of phase shifters
connected to the plurality of antennas thereof. A transmission beam of the base station
and a reception beam of the user equipment form a beam pair for the downlink. The
process of downlink beamforming training is a process which aims to find an optimal
beam pair consisting of an optimal base station transmission beam and an optimal user
equipment reception beam. Similarly, in the uplink, a base station reception beam
and a user equipment transmission beam also form a beam pair.
[0037] A Millimeter wave communication system has multiple modes of operation, such as a
point-to-point mode, a single-user mode, a multi-user mode, and the like. The point-to-point
mode can be used for backhaul among base stations, the single-user mode and multi-user
mode can be used for communication between a base station and one or more user equipments.
With respect to the implementation architecture, a pure analog beamforming architecture
(such as, a full-connection architecture, a sub-connection architecture without combining
with digital pre-coding), a full-connection analog-digital hybrid precoding, a sub-connection
analog-digital hybrid precoding, and the like can be included. However, no matter
which architecture is adopted, the configuration information of the base station and
the user equipment (for example, the configuration values of the phase shifters involving
the base station and the user equipment) can be only selected from a predefined analog
codebook, due to limitation from constraints for the apparatus. Such configuration
information may be referred to as weight vectors, which generally refer to configuration
values (e.g., phase values) for the plurality of phase shifters.
[0038] Such processing is mainly performed at respective radio frequency portions of a transmitting
end and a receiving end of a wireless communication system, and can be considered
as radio frequency analog processing.
Beamforming - Single User
[0039] The concept of beamforming technique will be exemplarily described below with reference
to figures.
[0040] FIGs. 4a and 4b show configurations of a base station and a user equipment in a single-user
system, respectively. As shown in FIG. 4a and FIG. 4b, in the user equipment and the
base station, each radio frequency chain is connected with a set of phase shifters,
and each phase shifter is connected to a corresponding antenna. The values (e.g.,
phase values) of a set of phase shifters may be indicated by a set of configuration
parameters, such as DFT vectors, also referred to as weight vectors or beam vectors.
Herein, we denote the weight vector of the base station as
f and the weight vector of the user equipment as
w. Since in the present example, a phase shifter only adjusts the phase of a signal
without changing its magnitude, the magnitude of each element in the weight vector
is one. In a millimeter wave communication system of this structure, since the number
of radio frequency chains is limited, the base station end and the user equipment
end cannot directly estimate the channel state information. Therefore, a common analog
beamforming scheme uses a method based on analog Tx/Rx codebooks. A codebook is a
collection of weight vectors. Let a codebook for the base station be F, with a size
of P (including P weight vectors), the codebook for the user equipment be W, with
a size of Q (including Q weight vectors), then the weight vector of the base station
must be selected from the codebook F for the base station, the weight vector of the
user equipment must be selected from the codebook W for the user equipment.
[0041] In millimeter wave communication between the base station and the user equipment,
a weight vector in the codebook which is to be particularly employed shall be determined
by beam training in advance. The beam training, for example, may employ a maximum
signal-to-noise (SNR) ratio criterion to determine weight vectors used to form optimal
beams, which may be expressed as:
[0042] Where
represents a downlink channel between the base station and the user equipment, W
is a candidate collection (codebook) for the weight vector of the user equipment,
and F is a candidate collection (codebook) for the weight vectors of the base station,
and
wopt, fopt are the determined optimal weight vector of the user equipment and of the base station,
respectively.
[0043] Due to large attenuation in a millimeter-wave channel path, the millimeter-wave multipath
channel has a small number of scatters, and a millimeter-wave channel H can usually
be modeled as:
[0044] Where
N and
M respectively represent the number of antennas equipped by the UE and the base station,
Ncl is the number of scatters,
Nray is the number of sub-paths included in each scatter, and
αi,l represents a channel coefficient of a corresponding scatter path,
aUE and
aBS represent antenna response vectors of the UE and the base station, respectively,
and θ and
φ are the horizontal and vertical angles of arrival, respectively.
[0045] For a uniform linear array (ULA), the antenna response vector is independent of the
vertical angle of arrival
φ, and can be expressed as
[0046] Where λ indicates wavelength, d indicates antenna pitch, and N indicates the number
of antennas.
[0047] For a W×H Uniform Planar Array (UPA), where W is the number of horizontal antennas,
H is the number of vertical antennas, the antenna response vector can be expressed
as:
[0048] Where,
is the horizontal antenna response vector,
is the vertical antenna response vector, and ⊗ is Kronecker Product (KP).
Beamforming - Multi-User hybrid precoding
[0049] For a multi-user scenario, considering a single-cell multi-user millimeter-wave large-scale
antenna system. The base station is equipped with W×H=M UPA antennas, and serves K
users at the same time, and each user is equipped with N antennas. A traditional large-scale
antenna system usually uses an all-digital precoding architecture to map K users'
data to M RF chains and antenna elements through an all-digital precoding matrix
and optimal precoding performance can be obtained. However, this architecture requires
M RF chains, resulting in high hardware complexity and high power consumption. Therefore,
a hybrid precoding architecture is generally considered in multi-user millimeter-wave
systems, which uses L (usually L = K, here assuming L = K) radio frequency chains
to connect the baseband digital signal to antenna units through phase shifters. FIGs.
5a and FIG. 5b show configurations of the base station and the user equipment in the
analog-to-digital hybrid precoding architecture, respectively.
[0050] As shown in FIG. 5a, the base station side employing the analog-to-digital hybrid
precoding architecture has a baseband digital precoder and an analog phase shifting
network. Under control of a controller, the baseband digital precoder obtains K-way
data streams as inputs, and the baseband digital precoder performs digital precoding
on K-way data streams, thereby eliminating interference between different data streams.
Then, K radio frequency chains process, such as up-convert, amplify, filter, etc.,
the data streams pre-coded by the digital precoder to generate radio frequency signals.
Generally, each of the K radio frequency chains corresponds to one UE.
[0051] K radio frequency chains are connected to the analog phase shifting network. Values
of individual phase shifters included in the analog phase shifting network constitute
an analog beamforming matrix F. In the matrix F, the kth column represents values
of a set of phase shifters connected to the kth radio frequency chain, expressed as
a weight vector
fk, and the weight vector
fk must be selected from a codebook
f for the base station.
[0052] FIG. 5b shows the configuration of a user side in a hybrid precoding architecture.
As shown in FIG. 5b, a user side is equipped with N antennas, and the signal received
by each antenna is input to a radio frequency chain after passing through a corresponding
phase shifter. Values of individual phase shifters constitute a weight vector
wk for the user equipment, which can be selected from a codebook
W for the user equipment. The radio frequency chain filters, amplifies, and downconverts
the input signals to obtain digital received signals.
[0053] In this example, the user side has a plurality of radio frequency chains. According
to the actual situation, it is also possible to adopt a design in which one radio
frequency chain is employed at the user side.
[0054] In a hybrid precoding architecture, a downlink transmission mode can be expressed
as:
[0055] Where x is the transmitted signal,
yk is the digital side receiving signal of the kth user,
Hk is the downlink channel matrix between the kth user and the base station, and F and
B are the analog precoding and digital precoding matrix, respectively, and the analog
precoding matrix F consists of analog transmission weight vectors (or beamforming
vectors) composed of phases of phase shifters connected to respective radio frequency
chains.
wk represents the analog reception weight vector of the kth user, and
nk represents the Gaussian white noise vector. Limited by the constraints of the apparatus,
the analog transmit/reception weight vector can only be selected from a pre-defined
simulation codebook, which is the simulation codebook F at the base station side and
the simulation codebook W at the user side respectively.
[0056] In the hybrid precoding architecture, the beam training is a process of determining
weight vectors of the base station and the user equipment from predetermined codebooks.
Taking downlink transmission as an example, the maximum signal-to-noise ratio criterion
can be expressed as:
[0057] Where
{wk,opt, fk,opt} indicates an optimal downlink weight vector for the k-th user.
Design for Phases-Shifting Network
[0058] It can be seen from Figures 4a, 4b, 5a and 5b that both the communication system
using analog precoding and the communication system using analog-digital hybrid coding
require beamforming training for transmission weight vectors and reception weight
vectors, to find optimal transmission weight vectors and reception weight vectors.
A weight vector is formed by values of a plurality of phase shifters connected to
antennas or an antenna array. Therefore, a phase shifting network composed of connection
of a plurality of phase shifters to a plurality of antennas is essential for beamforming.
For a phase-shifting network, the currently popular architectures are a full-connection
architecture and a sub-connection architecture. FIG. 6a and FIG. 6b show schematic
diagrams of a full-connection phase shifting network and a sub-connection phase shifting
network, respectively.
[0059] In a full-connection phase-shifting network, each RF chain can be connected to all
antennas via analog phase shifters. Therefore, the full-connection phase shifting
network can utilize a diversity gain of the entire antenna array to obtain better
precoding performance. As shown in FIG. 6a, in a full-connection phase-shifting network,
each radio frequency chain is connected to all antennas via phase shifters, wherein
each radio frequency chain is connected to a set of M phase shifters, so that in the
full-connection phase shifting network, there are K sets of phase shifters, and the
total number of phase shifters is K×M. Signals (K signals) output from individual
phase shifters in each set of phase shifters are added by an adder and supplied to
a corresponding antenna unit. If phases of phase shifters connected to the k-th radio
frequency chain create a M-dimensional beamforming vectors
a
M ×
K dimensional analog precoding matrix can be expressed as
[0060] In a sub-connection phase-shifting network, each radio frequency chain can be connected
to a part of the antennas via analog phase shifters. Usually, the antennas are evenly
distributed to K radio frequency chains. Each antenna unit is connected to only one
RF chain. Each RF chain in the sub-connection architecture can only utilize the diversity
gain of a part of the antenna array, resulting in a certain performance loss, but
at the same time the hardware complexity is greatly reduced. As shown in FIG. 6b,
in the sub-connection phase-shifting network, the output of each radio frequency chain
is connected to P phase shifters (P is an integer and P ≥ 1), and each phase shifter
is connected to one antenna unit. That is to say, in the case of having K radio frequency
chains, the number of antenna units M = K × P. Phase values of phase shifters connected
to the k-th radio frequency chain create a
dimensional beamforming vectors
and thus a
M ×
K dimensional analog precoding matrix can be expressed as:
[0061] Where
0M/K indicates a zero column vector with a length of
M/K.
[0062] The existing full-connection architecture performs well, but the hardware complexity
is high. The sub-connection architecture has a low hardware complexity, but the performance
loss is more serious, especially when the number of users increases. How to obtain
a reasonable compromise between hardware overhead and system performance is an urgent
problem to be solved in the industry. In addition, the full connection and sub-connection
architecture or hybrid precoding architecture does not consider the physical structure
of antennas. Therefore, it is important to consider the multi-antenna connection architecture
and precoding design method in the scenario where the base station is equipped with
a two-dimensional planar array antenna.
Hybrid connection architecture based on sub-array
[0063] In this regard, the applicant proposes an improved hybrid connection architecture
and a precoding design method.
[0064] In particular, in a wireless communication environment with large-scale antennas,
a plurality of antennas may be arranged as an antenna array, such as a one-dimensional
linear array, a two-dimensional planar array, or a curved surface array obtained by
bending a two-dimensional planar array in a horizontal or vertical direction. In the
case that multiple radio frequency chains share the antenna array, the antenna array
may include the same number of multiple antenna sub-arrays as the radio frequency
chains, each sub-array has several input terminals, and each input terminal may be
connected to one radio frequency chain.
[0065] It should be noted that in some examples of physical implementation, one sub-array
typically corresponds to a panel, and the division of antennas, the number and arrangement
of sub-arrays are generally predetermined. Under this premise, the radio frequency
chain usually has a one-to-one correspondence with the sub-array, and in some aspects
of the present disclosure, it is further proposed that the radio frequency chain also
utilizes sub-arrays other than the corresponding sub-array for communication.
[0066] In the context of the present disclosure, a first direction and a second direction
are mutually orthogonal directions in a tangent plane of the antenna array. In particular,
in the case where the antenna array is a two-dimensional planar array, the tangent
plane is the plane of the two-dimensional planar array per se, and the first direction
and the second direction are mutually orthogonal directions in the plane of the two-dimensional
planar array, for example, horizontal and vertical directions.
[0067] In an improved embodiment of the present disclosure, at least one radio frequency
chain may be in communication with a peer communication apparatus via a corresponding
antenna sub-array, and further may be in communication with the peer communication
apparatus via remaining sub-arrays other than the corresponding sub-array. Through
such communication, appropriate communication configuration parameters can be determined
for subsequent communication.
[0068] It should be noted that compared to an existing sub-connection phase-shifting network,
the hybrid connection architecture based on a number of sub-arrays of the present
application enables at least one radio frequency chain to utilize spatial diversities
of more than one antenna sub-arrays of multiple antenna sub-arrays, thereby enhancing
the beamforming gain. And compared to an existing full-connection architecture, the
number of phase shifters required by some embodiments of the hybrid connection architecture
based on a number of sub-arrays of the present application is significantly reduced.
[0069] According to one embodiment, an electronic equipment for a first communication apparatus
of a wireless communication system is proposed. The first communication apparatus
includes a number of atenna sub-arrays and a number of radio frequency chains. The
electronic equipment includes a processing circuitry configured to: for each of at
least one radio frequency chain of the number of radio frequency chains, perform a
first communication with a second communication apparatus in the wireless communication
system via a first one of the number of antenna sub-arrays corresponding to the radio
frequency chain, so that a first communication configuration parameter is determined;
and performs a second communication with the second communication apparatus via at
least one of remaining sub-arrays of the number of sub-arrays other than the corresponding
first sub-array, so that a second communication configuration parameter is determined,
wherein a communication configuration parameter for the radio frequency chain is determined
based on the first communication configuration parameter and the second communication
configuration parameter.
[0070] That is, both the first communication and the second communication can be performed
for at least one of all radio frequency chains, thereby determining a communication
configuration parameter for each radio frequency chain based on the first communication
configuration parameter and the second communication configuration parameter. And
for the remaining radio frequency chains, only the first communication can be performed,
such that communication configuration parameters for the radio frequency chains are
determined by the first communication configuration parameter.
[0071] In an exemplary implementation, in a case that a radio frequency chain only performs
a first communication via its corresponding antenna sub-array for determining a first
communication configuration parameter, a communication configuration parameter for
the radio frequency chain is the first communication configuration parameter, and
in a case that a radio frequency chain performs a first communication and a second
communcation for determining a first communication configuration parameter and a second
communication configuration parameter respectively, a communication configuration
parameter for the radio frequency chain can be obtained by synthesis of the first
configuration parameter and the second communication configuration parameter.
[0072] In some examples, the first communication configuration parameter may be predetermined
by the processing circuitry, or determined by an apparatus other than the first communication
apparatus and transmitted to the first communication apparatus.
[0073] Preferably, the first communication configuration parameter and the second communication
configuration parameter may be expressed in various forms, and the synthesis of the
first communication configuration parameter and the second communication configuration
parameter may be performed in a combination manner corresponding to the parameter
expression manner.
[0074] In some embodiments, both the first communication configuration parameter and the
second communication configuration parameter can be expressed in a vector form, such
that the synthesis of the first communication configuration parameter and the second
communication configuration parameter can be expressed as a combination of vectors,
such as a combination of vectors obtained in a well known manner in the art.
[0075] In a preferred implementation, in the second communication, one radio frequency chain
will perform a second communication with each sub-array of the number of sub-arrays
other than the corresponding sub-array, thereby determining the second communication
configuration parameter. In this way, each RF chain can utilize spatial diversities
of all antenna sub-arrays in a plurality of antenna sub-arrays such that the beamforming
gain is further optimized.
[0076] In another preferred implementation, in the second communication, one radio frequency
chain is not connected to all sub-arrays in the number of sub-arrays other than the
corresponding sub-array, but only to a specific number of sub-arrays therein. Thus,
although the spatial diversities of all antenna sub-arrays cannot be utilized, antenna
arrangement complexity and hardware overhead are appropriately reduced, thereby achieving
a more appropriate compromise between the gain and the complexity as well as hardware
overhead. In a particular design, selection of the specific number may be determined
based on factors on the first communication apparatus side, such as actual circuit
arrangement requirements, performance requirements, etc.
[0077] In yet another alternative implementation, in a number of radio frequency chains,
a specific number of radio frequency chains each only communicates with its corresponding
antenna sub-array, instead of the remaining antenna sub-arrays, and in addition to
their respective corresponding antenna sub-arrays, other radio frequency chains may
be in communication with a specific number of antenna sub-arrays or all antenna sub-arrays
in the remaining antenna sub-arrays, as described above. Thus, although spatial diversities
of all antenna sub-arrays cannot be utilized, the antenna arrangement complexity is
appropriately reduced, thereby achieving a more appropriate compromise between gain
and antenna complexity. In a particular design, selection of the specific number may
be determined based on factors on the first communication apparatus side, such as
actual circuit arrangement requirements, performance requirements, etc..
[0078] According to an embodiment, the first communication configuration parameter is determined
based on information on a communication channel state in the first communication received
from the second communication apparatus, and the second communication configuration
parameter is determined based on information on a communication channel state in the
second communication received from the second communication apparatus.
[0079] According to an embodiment, the first communication configuration parameter is a
communication configuration parameter that optimizes channel quality of the first
communication, and the second communication configuration parameter is a communication
configuration parameter that optimizes channel quality of the second communication.
[0080] According to an embodiment, the second communication configuration parameter comprises
second communication configuration parameters corresponding to at least one of remaining
sub-arrays in a plurality of sub-arrays other than the corresponding sub-array.
[0081] According to an embodiment, the first communication configuration parameter comprises
an analog beamforming vector when the radio frequency chain performs communication
via the corresponding first sub-array; and wherein the second communication configuration
parameter comprises analog beamforming vectors for at least one sub-array of remaining
sub-arrays of the plurality of sub-arrays other than the corresponding first sub-array
when the radio frequency chain performs communication via the at least one sub-array.
[0082] When performing the second communication, the radio frequency chain may perform communication
via the at least one sub-array of the remaining sub-arrays of the plurality of antenna
sub-arrays other than the corresponding sub-array by using the determined analog beamforming
vector included in the first communication configuration parameter. For example, the
radio frequency chain can perform the second communication by using the analog beamforming
vector determined by the radio frequency chain itself in the first communication process,
or can perfrom the second communication by using an analog beamforming vector determined
for a specific sub-array in the first communication process when the radio frequency
chain performs the second communication with the specific sub-array.
[0083] According to an embodiment, a phase shifter is disposed between a radio frequency
chain and a sub-array, wherein a phase shifter between a radio frequency chain and
a corresponding first sub-array is set by the first communication configuration parameter,
and phase shifters between the radio frequency chain and the remaining sub-arrays
are set by the second communication configuration parameter corresponding to the remaining
sub-arrays. That is, in an implementation, the first configuration parameter may further
include a phase of the phase shifter when the radio frequency chain communicates with
the corresponding sub-array, and the second configuration parameter may further include
phases of the phase shifters when the radio frequency chain communicates with the
remaining sub-arrays other than the corresponding sub-array.
[0084] According to an embodiment, the first communication configuration parameter includes
a power allocation factor for a corresponding first sub-array when the radio frequency
chain performs communiction via the corresponding first sub-array, and the second
communication configuration parameter includes power allocation factors for remaining
sub-arrays of the plurality of sub-arrays other than the corresponding sub-array when
the radio frequency chain performs communication via at least one of the remaining
sub-arrays.
[0085] Considering that beamforming vectors for respective sub-arrays can change once in
a longer period after determination thereof, weight parameters of the respective sub-arrays
for a particular communication chain (for example, other configuration parameters
other than to the beamforming vector) can be changed in a shorter period to compensate
for channel variations, thereby reducing reconfiguration overhead. Especially in an
example of the two-layer phase-shifting network, since the amplitude of motion of
the user equipment in vertical direction is generally small, a vertical beamforming
vector of each sub-array can change once in a longer period after determination thereof,
and a horizontal beamforming vector is adjusted in a shorter period according to the
latest channel condition.
[0086] To further facilitate understanding, an implementation of an embodiment of the present
invention where the first communication apparatus is a base station and the second
communication apparatus is a user equipment will be described below with reference
to FIG. 7a. FIG. 7a shows the base station having a processing circuitry 701, and
optionally, a communication configuration parameter synthesis unit 702 and a memory
703, as indicated by dashed boxes in the figure. Note that such description is just
as an example, instead of limitation.
[0087] According to an embodiment, the first communication configuration parameter determined
based on the first communication and/or the second communication configuration parameter
determined based on the second communication can be stored in the memory 703 of the
first communication apparatus. It should note that the memory 703 is not necessary
for the first communication apparatus 700. In some embodiments, the first communication
configuration parameter and second communication configuration parameter can be stored
in a storage device out of the first communication apparatus, or stored in different
storage devices separately, for example, stored in storage devices inside and outside
of the first communication apparatus 700 separately. In some embodiments, the first
communication configuration parameter and/or the second communication configuration
parameter may be directly transmitted to the communication configuration parameter
synthesis unit 702 to be combined into a communication configuration parameter for
a corresponding radio frequency chain.
[0088] The communication configuration parameter synthesis unit 702 can combine the input
first and second communication configuration parameters to determine a configuration
parameter for a radio frequency chain, but the communication configuration parameter
synthesis unit 702 is also optional. Alternatively, the first communication configuration
parameter and the second communication configuration parameter may be determined at
the second communication apparatus (in this example, the user equipment) or other
apparatus, and can be used to obtain the communication configuration parameter for
the radio frequency chain, and then the communication configuration parameter for
the radio frequency chain is transmitted from the user equipment to the first communication
apparatus (in this example, the base station).
[0089] In operation, the processing circuitry 701 can be used to configure signal transmission
of the base station such that each radio frequency chain performs a first communication
via a corresponding sub-array, respectively, so that the first communication configuration
parameter is determined, and such that each of the at least one radio frequency chain
can also perform a second communication with at least one sub-array other than its
corresponding sub-array so that the second communication configuration parameter is
determined.
[0090] In an embodiment, a phase shifting network composed of a plurality of phase shifters
is disposed between the plurality of radio frequency chains and the plurality of sub-arrays
of the base station. The processing circuitry 701 configures a radio frequency chain
to perform the first communication via the corresponding sub-array and the second
communication via the at least one sub-array other than the corresponding sub-array,
respectively, by configuring values of individual phase shifters in the phase-shifting
network. After the first communication configuration parameter and the second communication
configuration parameter are obtained, the first communication configuration parameter
may be used to set a value of a phase shifter between the radio frequency chain and
the corresponding sub-array when the radio frequency chain performs subsequent communication,
and the second communication configuration parameter can be used to set values of
phase shifters between the radio frequency chain and the at least one sub-array other
than the corresponding sub-array when the radio frequency chain performs subsequent
communication.
[0091] According to one embodiment, an electronic equipment for a second communication apparatus
of a wireless communication system is proposed. For example, the electronic equipment
can include a processing circuitry configured to: for a corrsponding radio frequency
chain of a first communication apparatus, acquire channel state information in a first
communication by the first communication apparatus performing with respect to the
second communication apparatus via a first one of a plurality of antenna sub-arrays
of the first communication apparatus corresponding to the radio frequency chain, so
that a first communication configuration parameter is determined based on the channel
state information in the first communication; and acquire channel state information
in a second communication by the first communication apparatus performing with respect
to the second communication apparatus via at least one of remaining sub-arrays of
the plurality of sub-arrays of the first communication apparatus other than the corresponding
first antenna sub-array, so that a second communication configuration parameter is
determined based on the channel state information in the second communication, wherein
a communication configuration parameter for the corresponding radio frequency chain
can be determined by using the first communication configuration parameter and the
second communication configuration parameter.
[0092] An exemplary description will be made below with reference to FIG. 7b, which shows
a schematic diagram of an electronic equipment for a second communication apparatus
in a wireless communication system in accordance with one embodiment of the present
invention. The second communication apparatus is for communicating with the communication
apparatus of FIG. 7a. For example, when the electronic equipment 700 of FIG. 7a is
located in a base station, the electronic equipment 710 of FIG. 7b is in a user equipment.
When the electronic equipment 700 of FIG. 7a is located in a user equipment, the electronic
equipment 710 of FIG. 7b is in a base station. An example in which the electronic
equipment of FIG. 7b is located in the user equipment will be described below.
[0093] As shown in FIG. 7b, the electronic equipment 710 can include a processing circuitry
711, and optionally a communication configuration parameter synthesis unit 712 and
a memory 713.
[0094] Memory 713 can be used to store the first communication configuration parameter and
the second communication configuration parameter, like memory 703 in Figure 7a. Like
memory 703, this memory 711 is also not necessary for the electronic equipment 710.
[0095] In operation, for a radio frequency chain of the first communication apparatus, the
first communication apparatus may perform the first communication to the second communication
apparatus via a first antenna sub-array of a plurality of antenna sub-arrays of the
first communication apparatus corresponding to the radio frequency chain, and performs
a second communication to the second communication apparatus via at least one of the
remaining antenna sub-arrays of the plurality of antenna sub-arrays other than the
corresponding first antenna sub-array. The processing circuitry 711 can determine
information about the channel states in the first communication and the second communication
based on the first communication and the second communication, respectively. The first
communication configuration parameter may be determined based on channel state information
in the first communication, and the second communication configuration parameter may
be determined based on channel state information in the second communication. In some
embodiments, the first communication configuration parameter and the second communication
configuration parameter optimize channel quality of the first communication and the
second communication, respectively. The determination of the first communication configuration
parameter and the second communication configuration parameter may be performed by
the processing circuitry 711 and then be transmitted to the first communication apparatus,
stored in the memory 713, or transmitted to the communication configuration parameter
synthesis unit 712.
[0096] The communication configuration parameter synthesis unit 712 obtains communication
configuration parameters for respective radio frequency chains based on the first
communication configuration parameter and the second communication configuration parameter,
and transmits them to the first communication apparatus under the control of the processing
circuitry 711. Also, the communication configuration parameter synthesis unit 712
is optional. As described above, the communication configuration parameters for the
respective radio frequency chains may be determined by the processing circuitry of
the first communication apparatus, or by other apparatuses than the first communication
apparatus and the second communication apparatus.
[0097] According to one embodiment, a method for a first communication apparatus of a wireless
communication system is proposed. The first communication apparatus is provided with
a number of atenna sub-arrays and a number of radio frequency chains. The mthod comprises:
for each of at least one radio frequency chain of the number of radio frequency chains,
performing a first communication with a second communication apparatus in the wireless
communication system via a first one of the number of antenna sub-arrays corresponding
to the radio frequency chain, so that a first communication configuration parameter
is determined; and performing a second communication with the second communication
apparatus via at least one of remaining sub-arrays of the number of sub-arrays other
than the corresponding first sub-array, so that a second communication configuration
parameter is determined, wherein a communication configuration parameter for the radio
frequency chain is determined based on the first communication configuration parameter
and the second communication configuration parameter.
[0098] According to one embodiment, a method for a second communication apparatus of a wireless
communication system is proposed. The mthod comprises: for a corrsponding radio frequency
chain of a first communication apparatus in the wireless communication system, acquiring
channel state information in a first communication by the first communication apparatus
performing with respect to the second communication apparatus via a first one of a
plurality of antenna sub-arrays of the first communication apparatus corresponding
to the radio frequency chain, so that a first communication configuration parameter
is determined based on the channel state information in the first communication; and
acquiring channel state information in a second communication by the first communication
apparatus performing with respect to the second communication apparatus via at least
one of remaining sub-arrays of the plurality of sub-arrays of the first communication
apparatus other than the corresponding first antenna sub-array, so that a second communication
configuration parameter is determined based on the channel state information in the
second communication.
[0099] According to an embodiment, a communication configuration parameter for the corresponding
radio frequency chain can be determined by using the first communication configuration
parameter and the second communication configuration parameter.
[0100] An exemplary implementation of a sub-array-based communication configuration process
in accordance with an embodiment will be described below with reference to the accompanying
drawings. It should be noted that, for ease of understanding, the following description
takes a two-dimensional planar antenna array as an example, but it should be noted
that the described embodiment is equally applicable to other types of antenna arrays,
for example, a shifting antenna array which can be divided into multiple sub-arrays,
curved antenna arrays, and the like. For example, in the case of a curved antenna
array, the plane mentioned in the following description is the tangent surface of
the curved antenna array.
[0101] FIG. 8 illustrates a flowchart of communication configuring performed in a base station
by using the electronic equipments of FIG. 7a and FIG. 7b in accordance with an embodiment
of the present invention.
[0102] As shown in FIG. 8, in step 801, the base station configures a phase shifting network
such that each of the at least one radio frequency chains of all radio frequency chains
performs a first communication via only its corresponding sub-array. Specifically,
in one example, a first radio frequency chain corresponds to a first sub-array, in
other words, data stream of the first radio frequency chain is mainly transmitted
by the first sub-array, and the base station utilizes weight vectors in an analog
transmission codebook for the first sub-array to configure phase shifters of the first
sub-array one by one so as to scan all transmitted beams.
[0103] At step 802, the base station transmits an orthogonal training sequence to the user
equipment based on the configuration at step 801. Specifically, the training sequences
transmitted by multiple radio frequency chains connected to the base station to multiple
user equipments are specific to radio frequency chains and orthogonal to each other,
so that the multiple radio frequency chains can perform transmission to multiple user
equipments in parallel. Each user equipment can receive a corresponding training sequence
signal through match filtering without interfering with each other.
[0104] At step 803, the user equipment uses the processing circuitry 712 to estimate equivalent
channel information from the respective radio frequency chains to the respective user
equipments based on the received training sequence. Specifically, in one example,
the user equipment configures phase shifters for its antenna array one by one by using
weight vectors in its analog reception codebook to scan all the reception beams so
as to receive beamforming training signals from the base station, thereby determining
a transmission-reception beam pair with an optimal reception condition from various
transmission-reception beam pairs, such as a pair with maximum RSRP (Reference Signal
Received Power)/RSRQ (Reference Signal Received Quality)/CQI of the received signal.
The user equipment can also calculate the channel condition of an equivalent channel
corresponding to the optimal transmission-reception beam pair, such as channel gain
and channel phase/direction, as part of the measurement result. In some alternative
examples, the user equipment provides channel conditions of equivalent channels corresponding
to all transmission-reception beam pairs as measurement results to the base station.
[0105] At step 804, the user equipment feeds back the equivalent channel estimation result
in step 803 to the base station to determine, by the base station, a first communication
configuration parameter for a corresponding radio frequency chain based on the equivalent
channel estimation result. Alternatively, the first communication configuration parameter
may also be determined by the user equipment or other apparatus and transmitted to
the base station. The first communication configuration parameter is typically a communication
configuration parameter that optimizes the channel quality of the first communication.
[0106] The first communication configuration parameter may include an optimal transmission
weight vector in the base station analog codebook. After the training is finally completed,
the base station may configure antenna phase values of sub-arrays corresponding to
the radio frequency chain for the user equipment by using the optimal transmission
weight vector, to transmit an optimal transmit beam for the user equipment. It can
be understood that the user equipment further configures phase values of its antenna
array according to an optimal receiving weight vector in the analog codebook to generate
an optimal reception beam corresponding to the optimal transmit beam, and performs
subsequent data signal communication based on the optimal beam pair. In an example
in which the user equipment includes the first communication configuration parameter
in the feedback result, in order to reduce the control signaling overhead, the first
communication configuration parameter may also be an optimal transmission weight vector
in the base station analog codebook or an indication of the optimal transmission beam,
such as an index. In a specific example, the transmission resources where each base
station transmission beam is located are different from each other, and the user equipment
feeds back the indication of the resource where the optimal transmit beam is located
to feed back the first communication configuration parameter.
[0107] The idea of the embodiment on which FIG. 8 is based is that data stream on one radio
frequency chain can be wirelessly transmitted through multiple sub-arrays to obtain
a spatial diversity gain. In an optimal implementation, further consideration is given
to how to coordinate multiple sub-arrays to carry data flows for a particular radio
frequency chain. In the optimal solution, the first communication configuration parameter
may also include a weight parameter for a corresponding sub-array. The weight parameter
may include an additional phase, and then the equivalent channel quality measurement
result includes the phase of the equivalent channel. The weight parameter may also
include a power allocation factor for the corresponding sub-array. The power allocation
factor is determined by normalizing total power of the radio frequency chain on individual
sub-arrays. The equivalent channel estimation result includes a gain for the equivalent
channel.
[0108] In one implementation, the phase and gain of the equivalent channel can be estimated
simultaneously in the same communication process. The optimal transmission weight
vector and sub-array additional phase, power allocation factor, etc. can be obtained
simultaneously in the same communication process. For example, when phase shifter
equipments in the phase shifting network of the base station antenna have sufficient
precisions, the sub-array additional phase and the transmission weight vector can
be implemented together by the phase shifting network.
[0109] In another implementation, the optimal transmission weight vector and sub-array additional
phase may also be obtained separately in different communication flows. For example,
the sub-array additional phase may be updated at a different frequency from that for
the optimal transmission weight vector, so they may be obtained in separate flows
that are performed in different cycles. As another example, when the precision of
the phase shifter equipment of the base station antenna for setting the transmission
weight vector cannot support, a separate additional phase shifter can be provided
to set the additional phase.
[0110] Moreover, in an exemplary implementation, a power allocation factor is not necessary,
so when estimating the first communication configuration parameter based on channel
quality, only the transmission weight vector and/or the additional phase are estimated
without estimating the gain of the equivalent channel.
[0111] At step 805, the base station configures the phase shifting network such that each
radio frequency chain performs a second communication via at least one of the plurality
of sub-arrays other than a corresponding sub-array.
[0112] At step 806, the base station transmits an orthogonal training sequence to the user
equipment based on the configuration at step 805.
[0113] At step 807, the user equipment uses the processing circuitry 712 to estimate equivalent
channel information from respective radio frequency chains to respective user equipments
based on the received training sequence.
[0114] At step 808, the user equipment feeds back the equivalent channel estimation result
in step 807 to the base station to determine, by the base station, the second communication
configuration parameter for a corresponding radio frequency chain based on the equivalent
channel estimation result. Likewise, as in step 804, the second communication configuration
parameter can also be determined by the user equipment or other apparatus and transmitted
to the base station.
[0115] The second communication configuration parameter may include information indicating
an optimal transmission weight vector in the second communication, and may further
include a weight parameter of a second sub-array for the transmission service of the
first radio frequency chain, and the weight parameter may include, for example, additional
phase configuration information, power allocation factor, etc. The additional phase
can be set as the conjugate of the equivalent channel phase provided by the second
sub-array for phase correction, to obtain additional spatial diversity gains to a
maximum extent. In this example, the additional phase can be superimposed on the basis
of the optimal transmission weight vector to configure phase shifters of the second
sub-array used of the first radio frequency chain for actual data transmission.
[0116] For each radio frequency chain, the second communication is performed for at least
one of a plurality of sub-arrays othere than a corresponding sub-array. In some embodiments,
the second communication can be performed for each of the plurality of sub-arrays
other than the corresponding sub-array. That is, when there are K radio frequency
chains and corresponding K sub-arrays, steps 805-808 in the second communication can
be repeated up to K-1 times for each radio frequency chain.
[0117] Similar to the first communication, in an exemplary implementation, the power allocation
factor in the second communication is not necessary, so when estimating the second
communication configuration parameter based on the channel quality, only the transmission
weight vector and the additional phase are estimated, without estimating the gain
of the equivalent channel.
[0118] Similarly, similar to the first communication, in an exemplary implementation, the
optimal transmission weight vector and the sub-array additional phase, the power allocation
factor, and the like in the second communication configuration parameter may be obtained
simultaneously in the same communication process, or may be obtained in separate communication
processes with different cycles.
[0119] The determining processes for the second communication configuration parameters in
steps 805 to 808 may be performed in various manners, for example, the determining
processes for the second communication configuration parameter may be configured just
like the first communication process, or may be performed in a simple manner by utilizing
the configuration result based on the first communication. The determination for the
second communication configuration parameter will be described in detail later with
reference to FIGS. 9a to 9c.
[0120] At step 809, the base station determines a communication configuration parameter
for each radio frequency chain based on the first communication configuration parameter
and the second communication configuration parameter. Alternatively, this operation
can also be completed by another apparatus other than the base station and the user
equipment, and then the communication configuration parameter for each radio frequency
chain is transmitted to the base station.
[0121] The above description of FIG. 8 is merely an example and is not intended to limit.
It should be noted that some implementations in the process described with respect
to FIG. 8, such as determination of the first communication configuration parameter,
the second communication configuration parameter, and the communication configuration
parameters in step 809, may be alternatively implemented as described above.
[0122] Figure 9a shows a schemetic diagram of a multi-sub-array based hybrid connection
structure of an examplary base station that can employ the communication configuration
process depicted in Figure 8, and Figure 9b shows a schemetic diagram of a phase-shifting
network for each antenna sub-array in the example base station as shown in Fig. 9a.
As shown in Figure 9a, a planar array antenna can be arranged as K sub-arrays corresponding
to K radio frequency chains, each input of a sub-array is connected to an RF chain
via an additional phase shifter and a radio frequency power amplifier., wherein the
radio frequency power amplifier is an optional component. Under this architecture,
each RF chain is connected to K sub-arrays, and the phases and amplitudes of signals
to individual sub-arrays are controlled by respective additional phase shifters and
RF power amplifiers. Assume that the additional phase of the phase shifter for the
k
th RF chain connecting to of the i
th sub-array is represented as
ejθk,i, and the normalized power allocation factor for the RF power amplifier is
αk,i.
[0123] Figure 9b illustrates a detailed implementation of the sub-arrays of Figure 9a. As
shown in Figure 9b, each sub-array has several input terminals, each of which can
be connected to a radio frequency chain. Each input terminal is connected to respective
antenna units via phase shifters. The phases for the phase shifters connected between
each input and all antenna units constitute a beamforming vector. It is assumed that
the k
th radio frequency chain transmits a corresponding beamforming vector through the i
th sub-array, denoted as
fk,i.
[0124] Figure 9c illustrates another detailed implementation of the sub-arrays of Figure
9a, where each sub-array is connected to only one set of phase shifters and is shared
by multiple radio frequency chains. As shown in Figure 9c, each sub-array has only
one input terminal, and each radio frequency chain is connected to the input terminals
of respective sub-arrays via additional phase shifters. For example, the radio frequency
chain 1 is connected to the sub-array 1 corresponding thereto via an additional phase
shifter 1-1, and is connected to the k-th sub-array in other sub-arrays via an additional
phase shifter 1-k. The phases of phase shifters connected between each input terminal
and all antenna elements constitute a beamforming vector. It is assumed that the kth
radio frequency chain transmits a corresponding beamforming vector through the i-th
sub-array, denoted as
fk,i.
[0125] The determination process of the second communication configuration parameter described
above will be described below with reference to FIGS. 9b and 9c.
[0126] In a specific example, such as Figure 9b, each sub-array is connected to multiple
sets of phase shifters and each set of phase shifters is exclusively owned by one
radio frequency chain. Specifically, steps 805 and 806 cause the first radio frequency
chain to transmit signals only via the second sub-array, and scan transmission weight
vectors for the phase shifters of the second sub-array for the first radio frequency
chain according to the analog codebook in a manner similar to the first communication
process, to transmit the training sequence; in step 807, the user equipment served
by the first radio frequency chain receives the scanning transmitted training sequence
by using an optimal reception weight vector determined by the first communication
process, and according to the reception situation, determines an optimal base station
transmission weight vector and an optimal channel gain, channel phase/direction, etc.
of the equivalent channel as equivalent channel states for feedbacking to the base
station. And so on, until the second communication between the first radio frequency
chain and a specific number of remaining sub-arrays, as well as the second communication
between other radio frequency chains and sub-array, are finished. It can be understood
that the second communication process is not optimal for signal transmission from
the first radio frequency chain to its user equipment, but can also provide a certain
spatial diversity gain.
[0127] According to an embodiment, the second communication, for example based on Figure
9b, can also be carried out in a simplified form. In one implementation, when performing
the second communication, a radio frequency chain performs communication by using
the determined analog beamforming vector for the radio frequency chain included in
the first communication configuration parameter via at least one of the remaining
sub-arrays of a plurality of sub-arrays other than the corresponding sub-array.
[0128] For example, the radio frequency chain performs the second communication by using
the determined optimal transmission weight vector corresponding to the radio frequency
chain included in the first communication configuration parameter via the sub-arrays
of the plurality of sub-arrays other than the corresponding sub-array. For each radio
frequency chain, the same optimal transmit beam is used for at least two sub-arrays.
[0129] In another example of a connection structure, such as corresponding to Figure 9c,
each sub-array is connected to only one set of phase shifters and is shared by multiple
radio frequency chains. Specifically, the first communication process determines an
optimal transmission weight vector of each primary service sub-array for each radio
frequency chain and an optimal reception weight vector of each user equipment itself.
On this basis, by way of example, step 805 causes the first radio frequency chain
to transmit signals only via a second sub-array, while the transmission weight vectors
of phase shifters for the second sub-array are fixed to optimal transmission weight
vectors used for the second radio frequency chain determined in the first communication
process; in step 806, the second sub-array transmits an orthogonal training sequence
for the first radio frequency chain by means of optimal transmission weight vectors
for the second radio frequency chain, and the user equipments served by the first
radio frequency chain perform reception by using the optimal reception weight vectors
determined in the first communication process, and in step 807, the channel gain,
channel phase/direction are determined according to the reception situation and be
fedback as equivalent channel states to the base station, until the second communication
between the first radio frequency chain and a specific number of remaining sub-arrays
as well as the second communication between the other radio frequency chains and sub-array
are completed. It will be understood that the second communication process may be
not optimal for signal transmission from the first radio frequency chain to its user
equipment, but may still provide a certain spatial diversity gain.
[0130] In this example, the second communication configuration parameter corresponds to
a weight parameter of a transmission service by the second sub-array for the first
radio frequency chain, and the weight parameter includes, for example, additional
phase configuration information, the additional phase may be set to the conjugate
of an equivalent channel phase provided by the second sub-array for performing phase
correction so as to obtain an additional spatial diversity gain to a maximum extent.
In this example, an additional phase shifter can be disposed between the first radio
frequency chain and the second sub-array to provide the additional phase described
above.
[0131] A precoding process will be described next with reference to the drawings. In a configuration
of a multi-sub-array based hybrid connection architecture to which the present disclosure
relates, the precoding process typically includes determining communication configuration
parameters, such as the first and second communication configuration parameters, according
to, for example, the processes described above, and performing communication between
the base station and the user equipment by utilizing the determined configuration
parameters, thereby determining a digital precoding matrix based on the fedback channel
communication status, such as PMI, CQI, etc., followed by precoding.
[0132] In an implementation, for the examplary base station in the multi-sub-array based
hybrid connection architecture in FIG. 9a, the precoding process can be divided into
three phases: 1. Determining a beamforming vector of each sub-array, that is, determining
the aforementioned beamforming vector
fk,i or
fk; 2. Determining additional phases of phase shifters and power allocation factors
of radio frequency power amplifiers for a radio frequency chain connecting to respective
sub-arrays, that is, determining the aforementioned
ejθk,i and
αk,i; 3. Determining a digital precoding matrix. Figure 10a illustrates an exemplary precoding
process for an examplary base station in the multi-subarray based hybrid connectivity
architecture.
[0133] It should be noted that the precoding process illustrated in Figure 10a is merely
exemplary, and such precoding process is particularly beneficial where the transmit
beamforming vector and the transmit configuration parameters, such as phase, of a
sub-array are varied/updated in different periods. For example, considering that beamforming
vectors of respective sub-arrays are determined to be changed once in a longer period,
weight parameters (for example, other configuration parameters other than the beamforming
vector) of the respective sub-arrays for a particular communication link can be changed
in a shorter period to compensate for channel variations, thereby reducing reconfiguration
overhead.
[0134] The process is described with the specific architecture corresponding to Figure 9b
as an example. In a first stage, step 1002, beamforming vectors for a plurality of
sub-arrays of each radio frequency chain are determined.
[0135] In the sub-array-based hybrid connection architecture, the channel matrix between
a target user of a radio frequency chain k, 1≤k≤K and all antennas is obtained by
combining channel matries for each sub-array, i.e.,
Hk =
[Hk,1,
Hk,2,
···,
Hk,K], where
Hk,i represents a channel matrix between the target user of the kth radio frequency chain
and the i-th sub-array. Assume that a receiption beam for the target user of the kth
radio frequency chain has been determined, denoted as
wk, then the design criterion for the beamforming vector
fk,i transmitted by the kth radio frequency chain via the i-th sub-array is such that
the gain of the equivalent channel
is maximum (where
represents the transpose of
wk), and can be selected from a predetermined codebook by a variety of beamforming training
algorithms. K beamforming vectors (corresponding to K sub-arrays respectively) shall
be determined for each of the radio frequency chains, and the training for each sub-array
can be performed by using the communication configuration process shown in FIG.8.
[0136] For example, the first communication configuration parameter and the second communication
configuration parameter obtained in steps 804 and 808 are respectively a beamforming
vector of a corresponding sub-array of each radio frequency chain and a beamforming
vector of each sub-array of each radio frequency chain other than the corresponding
sub-array. The specific implementation process may be: in the first communication,
the base station configures the phase shifting network so that the radio frequency
chain k transmits the orthogonal training sequence only via the kth sub-array (as
shown in steps 801-802). The corresponding user equipment measures the equivalent
channel quality based on the received orthogonal training sequence (as shown in step
803), and feeds back the equivalent channel quality measurement result to the base
station, to determine the beamforming vector
fk,k, 1 ≤ k ≤ K of the radio frequency chain k via the corresponding sub-array k (as shown in step
804). In the second communication, the base station configures the phase-shifting
network so that the radio-frequency link k transmits the orthogonal training sequence
via the k-1th sub-array (the first radio frequency chain sequentially transmits via
at most K-1 sub-arrays) (step 805∼806). Similarly, the corresponding user equipment
measures the equivalent channel quality (as shown in step 807) and feeds back the
equivalent channel quality measurement result to the base station, to determine the
beamforming vector of the radio frequency chain k via the k-1th sub-array.
fk,k-1,
2 ≤ k ≤ K, and
f1,K (as shown in step 808). And so on, all beamforming vectors can be trained through
the first communication and K-1 second communication.
[0137] As mentioned above, a simplified beam training method can be performed, in which,
in the first communication, a beamforming vector
fk,k,
1 ≤ k ≤ K transmitted by the radio frequency chain k via the kth sub-array is obtained, then
the determined beamforming vector is directly used as a vector used in the subsequent
second stage of processing, without performing the second communication operation.
That is, in the second stage of processing, in addition to the communication performed
by the radio frequency chain via the corresponding sub-array, the beam transmitted
by the radio frequency chain via other sub-arrays is also set to be the same as the
transmission beamforming vector of the radio frequency chain in the first communication,
i.e.,
fk,i = fk,k, i ≠ k. In this way, the operation in the second stage will be simplified.
[0138] It should be noted that the above description in conjunction with Figures 8 through
10 is mainly directed to a case where respective antenna sub-arrays are on the same
plane, as shown in Figure 11a. At this time, the radio frequency chain can perform
the first communication with respect to its corresponding sub-array and perform the
second communication with respect to other sub-arrays, respectively, without specifically
selecting a primary sub-array for the radio frequency chain.
[0139] In another implementation, multiple antenna sub-arrays may be not on the same plane.
Figure 11b illustrates an examplary case where a plurality of antenna sub-arrays are
not in the same plane, wherein two sub-arrays are tilted relative to the center sub-array.
It should be noted that there may be other forms for the case where multiple antenna
sub-arrays are not on the same plane, for example, a plurality of curved arrays may
be combined into a cylindrical form, a plurality of curved arrays may be combined
into a spherical form, and the like..
[0140] When multiple antenna sub-arrays are not on the same plane, a primary sub-array needs
to be selected for each radio frequency chain. In such a case, for each radio frequency
chain, the first communication and the K-1 second communication described above may
be employed to select the primary sub-array. It should be noted that in such a case,
the simplified beam training method described above cannot be applied, mainly because
the primary sub-array is usually determined after all communications have been performed,
while he transmission beam configuration parameters of the radio frequency chain for
each sub-array has been determined in the process. However, beamforming training in
a non-coplanar antenna sub-array as described above can achieve more spatial diversity
gain.
[0141] In accordance with an embodiment, in the communication with the first communication
apparatus, the second communication apparatus performs reception by means of an initial
set of reception configuration parameters or a particular set of reception configuration
parameters, wherein the reception configuration parameters of the second communication
apparatus are parameters related to directivity when the antenna at the receiver receives
a signal. The particular set of reception configuration parameters is a set of reception
configuration parameters in the plurality of sets of reception configuration parameters
of the receiver that optimizes the communication channel quality with the transmitter.
The particular set of reception configuration parameters is determined in such a manner
that in a case of the first communication apparatus employing each of a plurality
of sets of communication configuration parameters to configure the communication from
the first communication apparatus to the second communication apparatus, and the second
communication apparatus employing each of a plurality of sets of reception configuration
parameters to sequentially receive the communications, a set of reception configuration
parameters that optimizes the communication channel quality is selected as the particular
set of reception configuration parameters.
[0142] In a second stage, i.e., step 1004, additional phases and power allocation factors
for multiple sub-arrays of each radio frequency chain are determined.
[0143] The phase shifter phase and amplification factor for the radio frequency chain connecting
to each sub-array are determined by estimating the equivalent channel
Similarly, the equivalent channel estimation can be performed using the communication
configuration process shown in FIG. 8. At this time, the first communication configuration
parameter and the second communication configuration parameter obtained by steps 804
and 808 are respectively an additional phase and power allocation factor for the corresponding
sub-array of each radio frequency chain as well as an additional phase and power allocation
factor for each subarray of each radio frequency chain other than the corresponding
sub-array.
[0144] The specific implementation process may be: in the first communication, the base
station configures the phase shifting network such that the radio frequency chain
k performs transmission only via the kth sub-array (as in step 801), and each radio
frequency chain transmits an orthogonal training sequence by using the foregoing determined
transmission beamforming vector(as in step 802), the user estimates the equivalent
channel coefficient (as in step 803) and feeds it back to the base station to determine
additional phase and power allocation factor for the radio frequency chain k via the
corresponding sub-array k (step 804). In the second communication, the base station
configures the phase shifting network such that the radio frequency chain k performs
transmission only via the k-1th sub-array (the first radio frequency chain performs
transmission via the Kth sub-array) (as in step 805), and each radio frequency chain
transmits an orthogonal training sequence by using the foregoing determined transmission
beamforming vector (as in step 806), and the user estimates the equivalent channel
coefficient (as in step 807) and feeds it back to the base station to determine additional
phase and power allocation factor for the radio frequency chain k via the sub-array
k-1 (step 808). And so on, after the first communication and up to K-1 second communication,
all equivalent channel coefficients
can be obtained. The additional phase
θk,i for the kth RF chain connecting to the i-th sub-array is set to the conjugate of
the phase of the equivalent channel coefficient
i.e.,
The power allocation factor
αk,i is proportional to the equivalent channel gain, and the total power of each RF chain
is normalized, so
It should be noted that in step 1004, it may not be necessary to determine the power
allocation factor.
[0145] After determining the beamforming vector
fk,i, 1 ≤ i ≤ K, the additional phase
θk,i, and the power allocation factor
αk,i for the kth radio frequency chain via each sub-array, the transmission beamforming
vector of the kth radio frequency chain can be expressed as:
[0146] In the absence of power allocation, the transmission beamforming vector of the kth
radio frequency chain can be expressed as:
[0147] In an implementation, before step 1002, the base station may optionally perform step
1001 to broadcast each user equipment a first stage training information, for example,
a training sequence indication information for the user equipment, start time and
the end time of beamforming training (for example, the subframe number), the number
of times the training sequence is sent, and the like.
[0148] After determining beamforming vectors for a plurality of sub-arrays of each radio
frequency chain in step 1002, in step 1003, the base station may optionally configure
the phase values of the phase-shifting network based on the determined beam-forming
vectors, to carry out the operation in step 1004.
[0149] After determining additional phases and power allocation factors for the plurality
of sub-arrays of each radio frequency chain in step 1004, the base station can configure
values of the phase shifters and power amplifiers between each radio frequency chain
and the plurality of sub-arrays based on the determined additional phases and power
allocation factors in step 1005.
[0150] In a third stage, i.e., step 1006, the base station determines a digital precoding
matrix based on the result of the baseband equivalent channel estimation. The specific
implementation process may be, for example, as shown in the dotted line frame: in
step 1011, the base station transmits a reference signal such as a channel state information
reference signal (CSI-RS) to the user equipment; in step 1012, the user estimates
a channel state information based on the received reference signal. In step 1013,
each user feeds back the channel state information such as a Precoding Matrix Indicator
(PMI), a Channel Quality Indicator (CQI), and the like to the base station.
[0151] In step 1007, the base station performs digital precoding using the channel state
information fed back by each user to multiplex transmission resources while controlling
interference between users or determining a modulation coding scheme or the like for
user scheduling. The digital precoding design can use a zero-forcing algorithm, i.e.
[0152] Where
[Heq]i,j =
wiTHi,jfj,
Hi,j represents a channel matrix between the jth radio frequency chain and the ith user,
Λ represents a diagonal matrix for transmission power allocation between users.
[0153] Note that the power allocation factor may be an indication of a quantized form, similar
to CQI, and the additional phase may be an index value of a codeword selected from
a dedicated protocol codebook, similar to PMI, thereby reducing feedback overhead.
It is to be understood that the power allocation factor and the additional phase as
weight coefficients for respective sub-arrays have different functionalities from
the CQI and PMI. The weight coefficients are for setting the analog beam and for sub-array
weighting, and CQI and PMI are for a process, such as, resource scheduling, baseband
digital precoding, etc. after the analog beam is set.
[0154] The precoding process shown in Fig. 10a will be described below by taking the specific
architecture corresponding to Fig. 9c as an example. A greatly simplified process
can be implemented in the precoding operation in conjunction with the specific architecture
shown in Figure 9c.
[0155] Specifically, in the first stage, i.e., step 1002, in the first communication, the
beamforming vector
fk,k,
1 ≤ k ≤ K transmitted by the radio frequency chain k via the kth sub-array is obtained, and
then directly used as a vector used in the subsequent second stage of processing without
performing a second communication operation. That is, in the second stage of processing,
in addition to the radio frequency chain performing communication via the corresponding
sub-array, beams transmitted by the radio frequency chain via other sub-arrays are
also fixed to the beamforming vector determined in the first communication corresponding
to the other sub-arrays. In this way, the operation in the first stage will be simplified.
The operation in step 1003 can be performed as mentioned above, and will be not described
in detail.
[0156] In a second phase, i.e., step 1004, additional phases and power allocation factors
for multiple sub-arrays of each radio frequency chain are determined. The phase shifter
phase and amplification factor for the RF chain connecting to each sub-array are determined
by estimating the equivalent channel
Similarly, the equivalent channel estimation can be performed by using the communication
configuration process shown in FIG.8. Meanwhile, the first communication configuration
parameter and the second communication configuration parameter obtained by steps 804
and 808 are respectively the additional phase and power allocation factor of a corresponding
sub-array of each radio frequency chain, as well as additional phase and power allocation
factor of each subarray of each radio frequency chain other than the corresponding
sub-array.
[0157] Thereby, the transmission beamforming vector of the radio frequency chain similar
to the foregoing can be determined.
[0158] Subsequent processing of the third stage will proceed as described above with respect
to step 1006 and will not be described in detail herein. The operation in the step
1007 will proceed as described above and will not be described in detail herein.
[0159] It should be noted that the precoding process illustrated in FIG. 10a is merely exemplary,
and the precoding process of the present disclosure may also be performed in other
manners.
[0160] In one implementation, the first stage and the second phase of the precoding process
described above may be combined into one stage, that is, the transmission beamforming
vector, the additional phase, and the power allocation factor in the communication
can be determined together, not individually. In this case, its operation can be performed
using the communication configuration process shown in FIG.8. Meanwhile, At this time,
the first communication configuration parameter and the second communication configuration
parameter obtained by steps 804 and 808 are respectively the transmission beamforming
vector, the additional phase and power allocation factor of a corresponding sub-array
of each radio frequency chain, and the transmission beamforming vector, additional
phase and power allocation factor of each subarray of each radio frequency chain other
than the corresponding sub-array. This exemplary implementation is shown in Figure
10b.
[0161] In the precoding process shown in FIG. 10b, an optimal beamforming vector, a sub-array
additional phase, and the like when the radio frequency chain performs communication
via the corresponding sub-array is determined by 1102 and 1103. Then, the optimal
beamforming vector, the sub-array additional phase, and the like when the radio frequency
chain performs communication via the remaining sub-arrays is determined by 1104, 1105.
Thus, in 1106, a phase shifting network can be configured, including phase shifter
phase values, sub-array additional phases, and the like. Subsequent operations of
1006 and 1007 can be performed as previously described in connection with Figure 10a,
and the description will not be repeated here.
[0162] Similarly, in the precoding operation shown in Figure 10b, a simplified form of operation
can still be performed. For example, in the operations of 1102 and 1103, the beamforming
vector
fk,k,
1 ≤ k ≤ K transmitted by the radio frequency chain k via the kth sub-array is obtained, and
then the determined beamforming vector is directly used as a vector used in the subsequent
processing of 1104 and 1105, without determining a beamforming vector again. That
is, in the processing of 1104 and 1105, the beamforming vector transmitted by the
radio frequency chain through other sub-arrays is set as the transmission beamforming
vector of the radio frequency chain in the first communication, that is,
fk,i = fk,k,
i ≠ k.
[0163] Furthermore, another simplified form of processing can be performed in conjunction
with the architecture shown in Figure 9c. Wherein, in the processing of 1104 and 1105,
the beamforming vectors transmitted by the radio frequency chain via other sub-arrays
are set as the transmission beamforming vector via the sub-array in the first communication,
that is,
fk,i = fi,i, i ≠ k.
[0164] In the following, assuming that there are two radio frequency chains and two sub-arrays
(assuming K=2), it is described that the data communication antenna configuration
is determined by training in a hybrid connection architecture corresponding to the
simplified form of FIG. 9c, in which case the configuration can be determined in only
two rounds of training.
[0165] The first round: the radio frequency chain 1 transmits a training sequence to the
user equipment 1 (UE1) only via the primary sub-array 1, and a transmission beam vector
f1 and an equivalent channel
can be trained by scanning a codebook.
[0166] The radio frequency chain 2 transmits a training sequence to the user equipment 1
(UE2) only via the primary sub-array 2, and a transmission beam vector f2 and an equivalent
channel
can be trained by scanning a codebook.
[0167] The second round: the radio frequency chain 1 transmits the training sequence to
the UE1 only via the secondary sub-array 2, wherein the sub-array 2 fixedly uses the
beam vector f2, and UE1 detects an equivalent channel
to the sub-array 2;
[0168] The radio frequency chain 2 transmits the training sequence to the UE 2 only via
the secondary sub-array 1, wherein the sub-array 1 fixedly uses the beam vector f1,
and UE 2 detects an equivalent channel
to the sub-array 1.
[0169] Next, the phase value of the additional phase shifter 1-1 of the radio frequency
chain 1 is set to the conjugate
θ1,1 of the phase of the equivalent channel
and the phase value of the additional phase shifter 1-2 is set to the conjugate
θ1,2 of the phase of the equivalent channel
the phase value of the additional phase shifter 2-1 of the radio frequency chain
2 is set to the conjugate
θ2,1 of the phase of the equivalent channel
the phase value of the additional phase shifter 2-2 is set to the conjugate
θ2,2 of the phase of
[0170] Thus, the transmission configuration of the radio frequency chain 1 is completed.
The final transmission beamforming vector without power allocation can be expressed
as:
[0171] The transmission configuration of the radio frequency chain 2 is completed, and the
final transmission beamforming vector without power allocation can be expressed as:
Two-layer phase shifting network based on sub-array
[0172] In another embodiment, the present application also proposes a two-layer phase shifting
network design for a two-dimensional planar array antenna. In principle, a first direction
phase shifter and a second direction phase shifter may be arranged between antennas
in the two-dimensional planar array antenna of the communication system and radio
frequency chains, wherein each antenna is connected to the first direction phase shifter,
a set of first direction phase shifters connected to each row or column of antennas
are connected to a second direction phase shifter, and a constituted set of second
direction phase shifters are connected to the radio frequency chains. The electronic
equipment includes a processing circuitry configured to: configure configuration parameters
(eg, phase) of each of the set of second directional phase shifters, and configure
configuration parameters (eg, phase) of each of respective sets of first direction
phase shifters.
[0173] A two-layer phase shifting network of a two-dimensional planar antenna array is described
below in conjunction with Figures 12a, 12b and 13.
[0174] Considering a two-dimensional planar antenna array of W×H size, where W is the number
of horizontal antennas, H is the number of vertical antennas, and the index of the
antenna unit on the xth row and yth columns can be expressed as k = x·W+ y. Let
θk denote the phase shifting value on the antenna unit, i.e.
[f]k = ejθk, where f is the beamforming vector. Due to a Kronecker product property of the beamforming
vector of the two-dimensional planar antenna array, i.e.,
f = fh ⊗ fv, where f
h is a horizontal beamforming vector and f
v is a vertical beamforming vector, the following can be obtained:
[0175] Therefore, the phase shifting phase
θk on the kth antenna element can be obtained by a horizontal phase shift phase
θh,y and a vertical phase shift phase
θv,x, that is, the analog beamforming can be implemented by a two-layer phase shifting
network including a horizontal layer and a vertical layer.
[0176] According to the order of the horizontal phase shifting layer and the vertical phase
shifting layer, two kinds of phase shifting network architectures, that is, a vertical
priority structure and a horizontal priority structure, are proposed, as shown in
Figs. 12a and 12b. Taking the vertical priority structure as an example, each antenna
unit is first connected to a vertical phase shifter, so the number of vertical phase
shifters is equal to the number of antennas, that is, WH. Then, each column of vertical
phase shifters is connected to a horizontal phase shifter, so the number of horizontal
phase shifters is equal to the number of horizontal antennas, that is, W. Finally,
all horizontal phase shifters are connected to a RF chain. Due to the Kronecker product
structure of the beamforming vector, phase values of the vertical phase shifters constitute
a vertical beamforming vector, and respective columns should be identical, and phase
values of the horizontal phase shifters constitute a horizontal beamforming vector.
When the phase shifting network is configured to perform transmission using a beam
f = fh ⊗ fv, the kth element phase value
[f]k = ejθk of
f can be expressed as a product of a horizontal phase value
[fh]y =
ejθh,y and a vertical phase value
[fv]x = ejθv,x, where k = x·W+y, then, the phase shift value of the yth horizontal phase shifter
should be configured as
ejθh,y, and the phase shift value of the xth vertical phase shifter of each column of vertical
phase shifters should be configured as
ejθv,x.
[0177] The proposed two-layer phase-shifting network design has the following advantages:
- (1) The horizontal beam and the vertical beam can be independently controlled and
adjusted. In this architecture, the horizontal phase shifters and vertical phase shifters
are configured by means of independent controllers and thus can be adjusted independently.
Therefore, in the beam training process, the vertical beam and/or the horizontal beam
can also be scanned independently.
- (2) Reduce the complexity of the phase shifting network controller. The complexity
of the phase shifting network controller is determined by the size of the supported
codebook. In the traditional architecture, the codebook size is O(WH), and in the
proposed two-layer phase-shifting network design, the sizes of the horizontal codebook
and the vertical codebook are O(W) and O(H), respectively.
- (3) Low-precision phase shifters can be used. In an actual system, a phase shift value
of a phase shifter is quantized, for example, the phase-shifting phases supported
by a 2-bit quantized phase shifter is {0, π/2, π, -π/2}. The cost and power consumption
of the phase shifter increase rapidly with increasement of quantization precision,
so the usage of low-precision phase shifters, such as 1-bit quantized phase shifters,
can greatly reduce hardware complexity. In the conventional architecture, 2-bit quantized
phase shifters are usually used to ensure performance, and the number of 2-bit quantized
phase shifters required is WH. However, if 1-bit quantized phase shifters are used,
a serious performance loss will be caused. In the proposed two-layer phase shifting
network architecture, the horizontal phase shifting layer and the vertical phase shifting
layer can use phase shifters with different precisions. For example, in the vertical
priority structure , 1-bit phase shifters are used as vertical phase shifters, and
2-bit phase shifters are used as horizontal phase shifters, and W 2-bit phase shifters
and WH 1-bit phase shifters are required in total, and the hardware complexity is
greatly reduced.
[0178] In order to further illustrate the present disclosure, a more specific embodiment
is given below.
[0179] Consider a single-user millimeter-wave large-scale antenna system. The base station
is equipped with a UPA antenna array, and the number of antennas is M=W×H, where W=16
is the number of antennas in the width direction of the antenna array, and H=4 is
the number of antennas in the height direction of the antenna array. The user is equipped
with an NLA array of N=4. Figure 13 shows the performance comparison between the proposed
vertical-priority architecture and a traditional architecture, wherein the vertical-priority
architecture uses 1-bit quantized vertical phase shifters and 2-bit quantized horizontal
phase shifters, and the traditional architecture uses 2-bit quantized shift phasers
and 1-bit quantized phase shifters respectively. Compared to the traditional architecture
using 2-bit quantized phase shifters, the proposed vertical-priority architecture
significantly reduces hardware complexity; compared to the traditional architecture
using 1-bit quantized phase shifters, the proposed vertical-priority architecture
greatly improves the average reachable rate of the system.
[0180] The two-layer phase-shifting network design shown in Figures 12a and 12b shows only
a single RF chain. It should be understood that the proposed two-layer phase shifting
network design can also be extended to a multiple radio-frequency chain system.
[0181] In view of the above knowledge of the two-layer phase shifting network, the applicant
further proposes an improved sub-array-based two-layer phase shifting network.
[0182] According to an embodiment, an electronic equipment for a first communication apparatus
of a wireless communication system is proposed, comprising: a number of antenna sub-arrays,
each sub-array being a planar antenna array, each column or row in the sub-array corresponding
to one input terminal; a plurality of sets of first direction phase shifters, wherein
the first direction phase shifters in each set are disposed between input terminals
of the corresponding sub-arrays and a radio frequency chain, wherein each set of the
plurality of sets of first direction phase shifters is configured to adjust a first
configuration parameter, such as a first direction angle, of an antenna beam for transmitting
a corresponding radio frequency chain signal in a first direction in accordance with
a first control signal.
[0183] Thus, such an electronic equipment can advantageously implement RF chain-specific
first direction antenna beam adjustment.
[0184] Preferably, each sub-array can be configured to transmit antenna beams in a second
direction with different second configuration parameters (eg, a second direction angle),
the first direction and the second direction being orthogonal to each other.
[0185] Preferably, each antenna in the sub-array may be connected to a second direction
phase shifter, and the second direction phase shifter may be configured to adjust
the second direction angle of the antenna beam in the second direction according to
the second control signal.
[0186] Preferably, the precision of the second direction phase shifter may be lower than
that of the first direction phase shifter.
[0187] Preferably, each set of first direction phase shifters may be connected to only one
sub-array, each set of first direction phase shifters comprising at least the same
number of phase shifters as the input terminals of the corresponding sub-array.
[0188] Preferably, each set of first direction phase shifters is connectable to the number
of sub-arrays, each set of first direction phase shifters comprising at least the
same number of phase shifters as the total input terminals of the number of sub-arrays.
[0189] Thereby, it can be advantageous for a plurality of radio frequency chains sharing
the number of sub-arrays, thereby simplifying the connection while supporting one
radio frequency chain to enjoy spatial gains of a plurality of sub-arrays.
[0190] In a specific implementation, for example, each radio frequency chain can be connected
to multiple sub-arrays via a set of first direction phase shifters, and a switch/selector
can be disposed on the connection to each sub-array to assist in only using one sub-array
in the training process.
[0191] Preferably, the electronic equipment can be implemented as a base station, and further
includes a processing circuitry configured to sequentially generate a second control
signal and a first control signal for a beam training stage, and configure a second
direction phase shifter to sweep multiple second direction angles to transmit second
direction training beams, and then configures the first direction phase shifter to
sweep multiple first direction angles to transmit first direction training beams.
[0192] Preferably, the processing circuit is further configured to generate the first control
signal and the second control signal for the data communication stage based on the
beam training feedback from a second communication apparatus corresponding to each
radio frequency chain, and respectively configure the first direction phase shifter
and the second direction phase shifter to thereby transmit communication beams at
a specific first direction angle and a specific second direction angle.
[0193] Preferably, each column in the sub-array may correspond to one input terminal, the
first direction corresponding to a horizontal direction and the second direction corresponding
to a vertical direction.
[0194] In a specific implementation, the first direction phase shifter and the second direction
phase shifter may be electronic phase shifters or mechanical phase shifters. Accordingly,
configuring direction angles at which respective sub-array transmit antenna beams
may include an electrically tunnable configuring and a mechanical configuring. The
electrically tunnable configuring may be, for example, utilizing the method of training
beamforming vectors in step 1002 of Figure 10a to determine transmission beams of
sub-arrays in the first direction or the second direction. The electrically tunnable
configuring may also divide the azimuth angle of the first direction or the second
direction into a plurality of angles, each sub-array being configured as corresponding
to an angle. This division can be variable, semi-static depending on the manner of
electric phase shifter. For example, the azimuth angle of the first direction or the
second direction is initially divided uniformly, and then the azimuth angle of the
first direction or the second direction in which users are concentratedly distributed
is divided. In the case of a mechanical configuring, the operator can set direction
angles of different sub-arrays in the first direction or the second direction to be
different when laying the network. The mechanical configuration is also adjustable,
but requires manual adjustment.
[0195] Figure 14 illustrates an examplary hybrid connection architecture for a multi-user
wireless communication system employing a two-layer phase shifting network design.
The system includes K antenna sub-arrays, each sub-array uses two layers of phase
shifters, a phase of a vertical phase shifter is controlled by a vertical controller,
and a phase of a horizontal phase shifter is controlled by a horizontal controller.
The hybrid connection architecture differs from the hybrid connection architecture
employing a sub-connection phase-shifting network in that for an antenna sub-array
to which each radio-frequency chain is connected, the phase-shifting network consists
of a vertical layer and a horizontal layer.
[0196] According to an embodiment, a method for a first communication apparatus of a wireless
communication system is further proposed, the first communication apparatus comprising
a number of antenna sub-arrays, each sub-array being a planar antenna array, each
column or row in a sub-array corresponding to one input terminal; and a plurality
of sets of first direction phase shifters, the first direction phase shifters in each
set being disposed between input terminals of respective sub-arrays and a radio frequency
chain, the method comprising adjusting a first direction angle of an antenna beam
for transmitting a corresponding radio frequency chain signal in a first direction
by means of each set of the plurality of sets of first direction phase shifters according
to the first control signal.
[0197] By means of the above improved two-layer phase shifting network design based on antenna
sub-arrays, a first-direction antenna beam adjustment specific to a radio frequency
chain can be realized.
[0198] It should note that in the design of a two-layer phase shifting network scenario,
communication configuration parameters of a second communication apparatus in communication
with a first communication apparatus can also be set as described above. For example,
the second communication apparatus performs reception with an initial set of reception
configuration parameters or a specific set of reception configuration parameters,
such that the reception configuration parameters can be determined while the first
communication apparatus determines configuration parameters in the first direction
and configuration parameters in the second direction. The specific set of reception
configuration parameters is a set of reception configuration parameters in a plurality
of sets of reception configuration parameters of a receiver that optimize communication
channel quality with a transmitter. Preferably, the communication configuration parameters
of the second communication apparatus may also be divided into sub-configuration parameters
in two directions corresponding to the first direction parameter and the second direction
parameter of the first communication apparatus, and in a first direction related communication
and a second direction related communication, the sub-reception configuration parameters
of corresponding directions are determined respectively, thereby combining the determined
sub-reception configuration parameters of the two directions to obtain the final reception
configuration parameters.
Sub-array-based Hybrid Precoding + Two-layer Phase shifting network
[0199] The present application also proposes an improved sub-array-based hybrid connection
hybrid precoding architecture, in which a two-layer phase shifting network of antenna
sub-arrays is further considered.
[0200] As described in detail above, the hybrid-connection hybrid precoding architecture
includes multiple radio frequency chains and the same number of antenna sub-arrays
(set to K), each sub-array can be connected to multiple radio frequency chains, and
a phase shifter and an optional RF power amplifier can be provided between each sub-array
and each the RF chain. On this basis, each RF chain can be connected to each antenna
sub-array via a two-layer phase shifting network.
[0201] In the hybrid connection hybrid precoding architecture, the electronic equipment
of the first communication apparatus can still perform the first communication and
the second communication to determine the first communication configuration parameter
and the second communication configuration parameter, similar to the communication
flow as shown in FIG. 8. It should be noted, however, that in the determination of
each communication configuration parameter, sub-communication configuration parameters
corresponding to each layer of the two-layer phase-shifting network should be considered,
respectively.
[0202] According to an embodiment, an operation may be performed in each of the first communication
and the second communication by performing communication via a sub-array such that
the first sub-communication configuration parameter is determined, wherein the first
sub-communication configuration parameter is associated with a first direction relative
to a plane of the sub-array; and performing communication via the sub-array based
on the determined first sub-communication configuration parameter, such that a second
sub-communication configuration parameter is determined, wherein the second sub-communication
configuration parameter is associated with a second direction relative to the plane,
the second direction being orthogonal to the first direction. Thus, the first communication
configuration parameter is obtained by combining the first sub-communication configuration
parameter and the second sub-communication configuration parameter in the first communication,
and the second communication configuration parameter is obtained by combining the
first sub-communication configuration parameter and the second sub-communication configuration
parameter in the second communication.
[0203] In some embodiments, the first direction is a horizontal direction relative to a
plane of the antenna array, and the second direction is a vertical direction relative
to a plane of the antenna array. In still other embodiments, the first direction is
a vertical direction and the second direction is a horizontal direction.
[0204] In a particular implementation, a non-simplified beamforming training may be performed
for both the first communication and the second communication as discussed above in
connection with FIG. 8, for example, orthogonal training sequences are transmitted
for the first communication and the second communication, respectively, to perform
training, and in each of the first communication and the second communication, orthogonal
training sequences are separately transmitted for training the first sub-configuration
parameter and the second sub-configuration parameter, thereby obtaining a more accurate
and appropriate communication configuration parameter.
[0205] According to an embodiment, a simplified beamforming training may also be employed
to determine a communication configuration parameter.
[0206] Preferably, in the second communication, the second communication is performed by
using a beamforming vector included in the first sub-communication configuration parameter,
such that a third sub-configuration parameter is determined. Preferably, in the second
communication, the second communication is performed by using a beamforming vector
included in the first sub-communication configuration parameter and a beamforming
vector included in the second sub-communication configuration parameter, so that the
third sub-configuration parameter is determined.
[0207] Thus, the first communication configuration parameter includes the first sub-communication
configuration parameter associated with a first direction relative to a plane of the
plurality of antennas and a second sub-communication configuration parameter associated
with a second direction relative to the plane of the plurality of antennas, the first
direction and the second direction being orthogonal to each other; and the second
communication configuration parameter includes the first sub-communication configuration
parameter and the third sub-communication configuration parameter associated with
a second direction relaitve to the plane of the plurality of antennas.
[0208] It should be noted that the sub-communication configuration parameters described
above have similar meanings with the communication configuration parameters mentioned
in the full text. For example, the sub-communication configuration parameters may
also be a weight parameter for a corresponding sub-array. The weight parameter can
be a phase/additional phase, meanwhile the equivalent channel quality measurement
result is the phase of the equivalent channel. The weight parameter can also be a
power allocation factor for the corresponding sub-array, meanwhile the equivalent
channel estimation result is the gain of the equivalent channel. Moreover, as mentioned
above, the power allocation factor is not necessary.
[0209] According to an embodiment, a first direction phase shifter and a second direction
phase shifter are disposed between a radio frequency chain and a sub-array. The first
direction phase shifter and the second direction phase shifter between the radio frequency
chain and the corresponding sub-array are respectively set by the first sub-communication
configuration parameter and the second sub-communication configuration parameter in
the first communication. The first direction phase shifters and the second direction
phase shifters between the radio frequency chain and the remaining sub-arrays are
respectively set by the first sub-communication configuration parameter and the second
sub-communication configuration parameter in the second communication.
[0210] According to an embodiment, corresponding to the simplified beamforming scheme as
described above, the first direction phase shifter and the second direction phase
shifter between the radio frequency chain and the corresponding sub-array are respectively
configured by the first direction sub-communication configuration parameter and the
second direction sub-communication configuration parameter. The first direction phase
shifters and the second direction phase shifters between the radio frequency chain
and the remaining sub-array are respectively configured by the first direction sub-communication
configuration parameter and the third direction sub-communication configuration for
the remaining sub-arrays.
[0211] In this embodiment, a communication configuration parameter of a second communication
apparatus in communication with the first communication apparatus can also be set
as described above. For example, the second communication apparatus performs reception
with an initial set of reception configuration parameters or a specific set of reception
configuration parameters, such that the reception configuration parameter is determined
while the first communication apparatus determines a configuration parameter in the
first direction and a configuration parameter in the second direction. The specific
set of reception configuration parameters is a set of reception configuration parameters
in a plurality of sets of reception configuration parameters of a receiver that optimize
communication channel quality with a transmitter. Preferably, a communication configuration
parameter of the second communication apparatus may also be divided into sub-configuration
parameters in two directions corresponding to the first direction parameter and the
second direction parameter of the first communication apparatus, and in the first
direction related communication and the second direction related communication, sub-reception
configuration parameters in the corresponding directions are respectively determined,
thereby combining the determined sub-reception configuration parameters in the two
directions to obtain the final reception configuration parameters.
[0212] According to some embodiments, the first direction is a horizontal direction and
the second direction is a vertical direction. Each antenna in a sub-array is connected
to a horizontal phase shifter, and each row of horizontal phase shifters are connected
to a vertical phase shifter, and a constituted column of vertical phase shifters are
connected to a RF chain, and one column of vertical pahse shifters of each sub-array
have the same phase value.
[0213] According to further embodiments, the first direction is a vertical direction and
the second direction is a horizontal direction. Each antenna in the sub-array is connected
to a vertical phase shifter, and each column of vertical phase shifters are connected
to a horizontal phase shifter, and a constituted row of horizontal phase shifters
are connected to the radio frequency chain, one row of horizontal phase shifters of
each sub-array have the same phase values.
[0214] Specifically, the two-layer phase shifting network may adopt a vertical priority
structure or a horizontal priority structure. If a vertical priority structure is
used, the vertical phase shifting layer is shared by all radio frequency chains; if
a horizontal priority stucture is used, the horizontal phase shifting layer is shared
by all radio frequency chains.
[0215] Figures 15a and 15b show schematic diagrams of a hybrid connection hybrid precoding
architecture and a two-layer phase shifting network for each subarray therein in a
vertical priority structure, respectively.
[0216] In the vertical priority structure, each column of vertical phase shifters of each
sub-array shall have the same phase values, forming a vertical beamforming vector
for the sub-array, and a vertical beam for the k-th sub-array is represented by
fv,k. In addition, a phase value of a horizontal phase shifter connecting a certain RF
chain and the sub-array constitutes a horizontal beamforming vector transmitted by
the RF chain using the sub-array, and
fh,k,j is used to represent a horizontal beam transmitted by the kth RF chain via the jth
sub-array. The corresponding beamforming vector transmitted by the kth radio frequency
chain via the jth sub-array is
fk,j =
fh,k,j⊗fv,k. There also exists an additional phase
θk,j when the kth RF chain is connected to the jth sub-array, which can be implemented
by a horizontal phase shifter without additional hardware overhead. In addition, in
the case of supporting power allocation, before the kth RF chain is connected to the
jth sub-array, an additional RF power amplifier needs to be configured, and the normalized
amplification factor is represented by
αk,j.
[0217] The number of phase shifters required in a traditional full connection architecture
is KWH, the number of phase shifters required for a sub-connection architecture is
WH, and the number of phase shifters required for the proposed hybrid connection architecture
is WH+KW. The complexity is greatly reduced compared to the full connection architecture.
[0218] Based on this hybrid connection architecture, various precoding processes can be
designed.
[0219] As an example, Figure 16 illustrates an examplary precoding design flow. Similar
to Fig. 10a, the precoding design process also includes three stages: 1. Determining
a beamforming vector for each subarray (step 1602); 2. Determining an additional phase
of a phase shifter and a power allocation factor of a radio frequency power amplifier
for a radio frequency chain connecting to each subarray (step 1604); 3. Determining
a digital precoding matrix (step 1606). Besides the particular implementation process
of step 1602 being somewhat different from that in Fig. 10a, the other steps 1601,
1603∼1607 can be implemented completely with reference to the corresponding steps
1001, 1003∼1007 in FIG. 10a, and the details are not described here. An exemplary
implementation of the step 1602 of determining a beamforming vector for each sub-array
is specifically described below, as shown by the dashed box in Figure 16, wherein
it is assumed that the system employs the vertical-priority hybrid connection architecture
shown in Figures 15a and 15b.
[0220] Sub-array beam design is performed in steps 1611-1615. The base station is configured
such that the kth radio frequency chain performs transmission only via the kth sub-array,
and a beamforming training process is performed to configure a horizontal beamforming
vector
fh,k,k and a vertical beamforming vector
fv,k (
1 ≤
k ≤
K) for each radio frequency chain connecting to a corresponding sub-array, and a reception
beamforming vector
wk of a corresponding user. This step is identical to the beamforming training process
in the traditional sub-connection architecture, and can employ existing beamforming
training algorithms, such as exhaustive search, single feedback search, and the like.
Each RF chain transmits an orthogonal training sequence during training to support
simultaneous training. After the user estimates an optimal base station transmission
beam between the user and the corresponding radio frequency chain, the index of the
transmission beam is fed back.
[0221] The horizontal beam design is performed in steps 1616∼1619. Specifically, K-1 training
stages are included. In each training stage, the base station is configured such that
the kth radio frequency chain performs transmission via only the jth,
1 ≤
j ≤
K,
j ≠
k sub-array, and the beamforming training process is carried out to configure a horizontal
beamforming vector
fh,k,j,
k ≠
j for each RF chain connecting to other sub-arrays. Each radio frequency chain transmits
an orthogonal training sequence to sweep alternate horizontal transmission beams in
a horizontal codebook. At each training stage, after the user estimates an optimal
horizontal transmission beam between it and a corresponding radio frequency chain,
the index of the horizontal transmission beam is fed back.
[0222] Those skilled in the art will recognize that the process for determining a beamforming
vector for each sub-array performed in steps 1611 to 1619 is obtained by combining
the multi-sub-array based communication configuration process shown in FIG. 8 and
the two-layer phase shifting network design proposed by the present application.
[0223] Also, a simplified beamforming training method can be performed. Since optimal horizontal
beams transmitted by the same radio frequency chain via different sub-arrays tend
to be the same,
fh,k,j,
k ≠
j can be directly set to
fh,k,k, thus steps 1616∼1619 can be omitted.
[0224] In step 1620, based on the horizontal beamforming vector
fh,k,k and the vertical beamforming vector
fv,k (
1 ≤
k ≤
K) for a sub-array k corresponding to the kth radio frequency chain and the horizontal
beamforming vector
fh,k,j,
k ≠
j for another sub-array j,
1 ≤
j ≤
K,
j ≠
k obtained in steps 1611 to 1619, it can be determined that a corresponding beamforming
vector transmitted by the radio frequency chain k via the j-th sub-array is
fk,j =
fh,k,j⊗
fv,k.
[0225] According to an embodiment, the beamforming vector determining step 1602 may be merged
with the determination of the additional phase and power allocation factor 1604, and
accordingly, step 1603 and step 1605 may also be merged. Figure 17 shows an examplary
implementation for determining beamforming vectors and additional phases and power
allocation factors after merging. FIG. 17 is substantially the same as steps 1611-1620
in FIG. 16 except that in step 1704, the user also needs to feed back the gain and
phase of the equivalent channel
corresponding to the transmission beam; in step 1709, the user also needs to feed
back the gain and phase of the equivalent channel
corresponding to the horizontal transmission beam; in step 1710, not only the beamforming
vectors of the plurality of sub-arrays of each radio frequency chain are determined,
but also the additional phase and power allocation factor of each sub-array are determined.
[0226] When the aforementioned simplified beamforming training method is employed, the beamforming
vector determining step 1602 can also be merged with the determination of the additional
phase and power allocation factor 1604. Figure 18 illustrates an examplary implementation
of determination of the beamforming vector and determination of the additional phase
and power allocation factor being merged when the simplified beamforming training
method is employed. FIG.18 is substantially the same as steps 1701-1710 in FIG. 17,
except that in step 1805, the base station configures a horizontal phase shifting
network and a vertical phase shifting network for all sub-arrays including the other
sub-arrays directly according to the optimal transmission beam fedback in step 1804;
accordingly, the user no longer needs to determine the optimal horizontal transmission
beam in step 1808, nor feed back the optimal horizontal transmission beam in step
1809; in addition, in step 1810, only the additional phase and power allocation factor
for each subarray is determined, because the beamforming vector for each sub-array
has been determined in step 1805.
[0227] In order to further illustrate the present disclosure, a more specific embodiment
is given below.
[0228] Considering a millimeter-wave multi-user scenario, the base station is equipped with
a UPA array of W=16×H=4, serving K=4 users simultaneously, the base station antennas
are divided into K=4 4×4 sub-arrays, and the user terminal is equipped with N= 4 ULA
arrays. In this configuration, the full connection architecture requires KWH = 256
phase shifters, the sub-connection architecture requires WH = 64 phase shifters, and
the proposed hybrid connection architecture requires WH + KW = 128 phase shifters.
The simulation results of a user average reachable rate for the three architectures
are shown in Figure 19. It can be seen that the performance of the proposed hybrid
connection architecture is between that of the full connection architecture and the
sub-connection architecture, and the performance in a case of allowing power allocation
is better than that in a case of no power allocation.
<Application example>
[0229] The technique of the present disclosure can be applied to various products. For example,
the BS may be implemented as any type of evolved Node B (eNB), such as a macro eNB
and a small eNB. A small eNB may be an eNB that covers cells smaller than the macro
cells, such as a pico eNB, a micro eNB, or a home (femto) eNB. Alternatively, the
BS may be implemented as any other type of BS, such as a NodeB and a Base Transceiver
Station (BTS). The BS may comprise: a main unit that is configured to control wireless
communication, also referred to as a BS apparatus, such as the electronic equipments
700 and 710 as described in the present application; and one or more remote wireless
headends (RRHs) that are located in different locations from the main unit. In addition,
various types of terminals described below may operate as a BS by temporarily or semi-permanently
performing the functions of a BS.
[0230] For example, the UE may be implemented as a mobile terminal such as a smart phone,
a tablet personal computer (PC), a notebook PC, a portable game terminal, a portable/dongle
type mobile router, and a digital camera, or an on-board terminal such as a car navigation
apparatus. The UE may also be implemented as a terminal performing machine-to-machine
(M2M) communication, also referred to as a machine type communication (MTC) terminal.
In addition, the UE may be a wireless communication module installed on each of the
aforementioned terminals, such as an integrated circuit module including a single
wafer, such as the electronic equipments 700 and 710 as described in the present application.
[0231] Fig. 20 shows an example of a hardware configuration of an electronic equipment according
to the present invention.
[0232] The central processing unit (CPU) 2001 functions as a data processing unit that performs
various types of processing based on programs stored on a read only memory (ROM) 2002
or a storage unit 2008. For example, the CPU 2001 performs processing based on the
aforementioned sequence. A random access memory (RAM) 2003 stores programs, data,
and the like executed by the CPU 2001. The CPU 2001, the ROM 2002, and the RAM 2003
are connected to each other via a bus 2004.
[0233] The CPU 2001 is connected to the input and output interface 2005 via a bus 2004,
and an input unit 2006 composed of various switches, a keyboard, a mouse, a microphone,
and the like, and an output unit 2007 composed of a display, a speaker, and the like
are connected to the input and output interface 2005. For example, the CPU 2001 executes
various types of processing in response to an instruction input from the input unit
2006, and outputs the processing result to the output unit 2007.
[0234] The storage unit 2008 connected to the input and output interface 2005 is constituted
by, for example, a hard disk, and stores thereon programs and various types of data
executed by the CPU 2001. The communication unit 2009 communicates with an external
apparatus via a network such as the Internet or a local area network.
[0235] The drive 2010 connected to the input and output interface 2005 drives a removable
medium 2011 such as a magnetic disk, an optical disk, a magneto-optical disk, or a
semiconductor memory (for example, a memory card), and acquires each of the contents
such as content and key information recorded thereon. Class data. For example, by
using the acquired content and key data, the CPU 2001 performs processing such as
beamforming training for wireless communication based on the reproduction program.
[0236] The methods and systems of the present invention may be implemented in a number of
ways. For example, the methods and systems of the present invention can be implemented
in software, hardware, firmware, or any combination of software, hardware, and firmware.
The above-described sequence of steps for the method is for illustrative purposes
only, and the steps of the method of the present invention are not limited to the
order specifically described above unless otherwise specifically stated. Moreover,
in some embodiments, the invention may also be embodied as a program recorded in a
recording medium, the program comprising machine readable instructions for implementing
the method according to the invention. Thus, the invention also covers a recording
medium storing a program for performing the method according to the invention.
[0237] Heretofore, the beamforming training method and the electronic equipment for the
base station and the user equipment according to the present invention have been described
in detail. In order to avoid obscuring the inventive concept, some details known in
the art are not described. Those skilled in the art can fully understand how to implement
the technical solutions disclosed herein according to the above description.
[0238] The methods and systems of the present invention may be implemented in a number of
ways. For example, the methods and systems of the present invention can be implemented
in software, hardware, firmware, or any combination of software, hardware, and firmware.
The above-described sequence of steps for the method is for illustrative purposes
only, and the steps of the method of the present invention are not limited to the
order specifically described above unless otherwise specifically stated. Moreover,
in some embodiments, the invention may also be embodied as a program recorded in a
recording medium, the program comprising machine readable instructions for implementing
the method according to the invention. Thus, the invention also covers a recording
medium storing a program for performing the method according to the invention.
[0239] While the invention has been described in detail with reference to the specific embodiments
of the present invention, it should be understood that It will be appreciated by those
skilled in the art that the above embodiments may be modified without departing from
the scope and spirit of the invention. The scope of the invention is defined by the
appended claims.
1. An electronic equipment for a first communication apparatus of a wireless communication
system, comprising:
a number of antenna sub-arrays, each sub-array being a planar antenna array, each
column or row in the sub-array corresponding to one input terminal;
a plurality of sets of first direction phase shifters, wherein the first direction
phase shifters in each set are disposed between input terminals of the corresponding
sub-arrays and a radio frequency chain,
wherein each set of the plurality of sets of first direction phase shifters is configured
to adjust a first direction angle of an antenna beam for transmitting a corresponding
radio frequency chain signal in a first direction in accordance with a first control
signal.
2. The electronic equipment of claim 1 wherein each sub-array is configured to transmit
antenna beams in a second direction with a different second direction angle, the first
direction and the second direction being orthogonal to each other.
3. The electronic equipment of claim 2, wherein each antenna in the sub-array is connected
to a second direction phase shifter, and the second direction phase shifter is configured
to adjust the second direction angle of the antenna beam in the second direction according
to the second control signal.
4. The electronic equipment of claim 3, wherein the second direction phase shifter has
a lower precision than the first direction phase shifter.
5. The electronic equipment according to any one of claims 1 to 4, wherein each set of
first direction phase shifters is connected to only one sub-array, each set of first
direction phase shifters comprising at least the same number of phase shifters as
the input terminals of the corresponding sub-array.
6. The electronic equipment of any of claims 1-4, wherein each set of first direction
phase shifters is connectable to the number of sub-arrays, each set of first direction
phase shifters comprising at least the same number of phase shifters as the total
input terminals of the number of sub-arrays.
7. The electronic equipment of claim 3, wherein the electronic equipment is implemented
as a base station, and further includes a processing circuitry configured to sequentially
generate a second control signal and a first control signal for a beam training stage,
and configure a second direction phase shifter to sweep multiple second direction
angles to transmit second direction training beams, and then configure the first direction
phase shifter to sweep multiple first direction angles to transmit first direction
training beams.
8. The electronic equipment of claim 7, wherein the processing circuit is further configured
to generate a first control signal and a second control signal for a data communication
stage based on the beam training feedback from a second communication apparatus corresponding
to each radio frequency chain, and respectively configure first direction phase shifters
and second direction phase shifters to thereby transmit communication beams at a specific
first direction angle and second direction angle.
9. The electronic equipment according to claims 2-8, wherein each column in a sub-array
corresponds to one input terminal, the first direction corresponding to a horizontal
direction and the second direction corresponding to a vertical direction.
10. An electronic equipment for a first communication apparatus of a wireless communication
system, wherein the first communication apparatus includes a number of atenna sub-arrays
and a number of radio frequency chains, the electronic equipment includes
a processing circuitry configured to: for each of at least one radio frequency chain
of the number of radio frequency chains,
perform a first communication with a second communication apparatus in the wireless
communication system via a first one of the number of antenna sub-arrays corresponding
to the radio frequency chain, so that a first communication configuration parameter
is determined; and
performs a second communication with the second communication apparatus via at least
one of remaining sub-arrays of the number of sub-arrays other than the corresponding
first sub-array, so that a second communication configuration parameter is determined,
wherein a communication configuration parameter for the radio frequency chain is determined
based on the first communication configuration parameter and the second communication
configuration parameter.
11. The electronic equipment of claim 10, wherein the first communication configuration
parameter is determined based on information on a communication channel state in the
first communication received from the second communication apparatus, and
the second communication configuration parameter is determined based on information
on a communication channel state in the second communication received from the second
communication apparatus.
12. The electronic equipment of claim 10, wherein the first communication configuration
parameter is a communication configuration parameter that optimizes channel quality
of the first communication, and the second communication configuration parameter is
such that the second communication Communication configuration parameters with optimal
channel quality.
13. The electronic equipment of claim 10, wherein the second communication configuration
parameter comprises second communication configuration parameters corresponding to
at least one of remaining sub-arrays in the numbern of sub-arrays other than the corresponding
first sub-array.
14. The electronic equipment of claim 10, wherein the first communication configuration
parameter comprises an analog beamforming vector when the radio frequency chain performs
communication via the corresponding first sub-array; and wherein the second communication
configuration parameter comprises analog beamforming vectors for at least one sub-array
of remaining sub-arrays of the number of sub-arrays other than the corresponding first
sub-array when the radio frequency chain performs communication via the at least one
sub-array.
15. The electronic equipment according to claim 10, wherein, upon performing the second
communication, the radio frequency chain performs communication via the at least one
sub-array of the remaining sub-arrays of the number of antenna sub-arrays other than
the corresponding sub-array by using the determined analog beamforming vector included
in the first communication configuration parameter.
16. The electronic equipment of claim 10, wherein a phase shifter is disposed between
a radio frequency chain and a sub-array, wherein a phase shifter between a radio frequency
chain and a corresponding first sub-array is set by the first communication configuration
parameter, and phase shifters between the radio frequency chain and the remaining
sub-arrays are set by the second communication configuration parameters corresponding
to the remaining sub-arrays.
17. The electronic equipment of claim 10, wherein the first communication configuration
parameter includes a first sub-communication configuration parameter associated with
a first direction relative to a tangent plane of antenna sub-arrays and a second sub-communication
configuration parameter associated with a second direction relative to the plane of
the tangent plane of antenna sub-arrays, the first direction and the second direction
being orthogonal to each other; and
wherein the second communication configuration parameter includes the first sub-communication
configuration parameter and a third sub-communication configuration parameter associated
with a second direction relaitve to the tangent plane of the antenna sub-arrays.
18. The electronic equipment of claim 17, wherein
in the second communication, the second communication is performed by using a beamforming
vector included in the first sub-communication configuration parameter, such that
the third sub-configuration parameter is determinedd.
19. The electronic equipment of claim 17, wherein
in the second communication, the second communication is performed by using a beamforming
vector included in the first sub-communication configuration parameter and a beamforming
vector included in the second sub-communication configuration parameter, so that the
third sub-configuration parameter is determined.
20. The electronic equipment of claim 17, wherein a first direction phase shifter and
a second direction phase shifter are disposed between a radio frequency chain and
a sub-array,
wherein the first direction phase shifter and the second direction phase shifter between
the radio frequency chain and the corresponding sub-array are respectively set by
the first sub-communication configuration parameter and the second sub-communication
configuration parameter; and
the first direction phase shifters and the second direction phase shifters between
the radio frequency chain and each of the remaining sub-arrays are respectively set
by the first sub-communication configuration parameter and the third sub-communication
configuration parameter for the remaining sub-array.
21. The electronic equipment of claim 17, wherein the first direction is a horizontal
direction and the second direction is a vertical direction, and
wherein each antenna in a sub-array is connected to a horizontal phase shifter, and
each row of horizontal phase shifters are connected to a vertical phase shifter, and
a constituted column of vertical phase shifters are connected to a RF chain, and
wherein one column of vertical pahse shifters of each sub-array have the same phase
value.
22. The electronic equipment of claim 17, wherein the first direction is a vertical direction
and the second direction is a horizontal direction, and
wherein each antenna in the sub-array is connected to a vertical phase shifter, and
each column of vertical phase shifters are connected to a horizontal phase shifter,
and a constituted row of horizontal phase shifters are connected to the radio frequency
chain, and
wherein one row of horizontal phase shifters of each sub-array have the same phase
values.
23. The electronic equipment of claim 10, wherein in each of the first communication and
the second communication:
performing communication via a sub-array such that the first sub-communication configuration
parameter is determined, wherein the first sub-communication configuration parameter
is associated with a first direction relative to a tangent plane of an atenna sub-array;
performing communication via the sub-array based on the determined first sub-communication
configuration parameter, such that a second sub-communication configuration parameter
is determined, wherein the second sub-communication configuration parameter is associated
with a second direction relative to the tangent plane, the second direction being
orthogonal to the first direction,
wherein the first communication configuration parameter is obtained by combining the
first sub-communication configuration parameter and the second sub-communication configuration
parameter in the first communication, and the second communication configuration parameter
is obtained by combining the first sub-communication configuration parameter and the
second sub-communication configuration parameter in the second communication.
24. The electronic equipment of claim 13, wherein the first communication configuration
parameter includes a power allocation factor for a corresponding first sub-array when
the radio frequency chain performs communiction via the corresponding first sub-array,
and the second communication configuration parameter further includes power allocation
factors for remaining sub-arrays of the number of sub-arrays other than the corresponding
sub-array when the radio frequency chain performs communication via at least one of
the remaining sub-arrays.
25. The electronic equipment of claim 24, wherein the power allocation factor is determined
by normalizing total power of the radio frequency chain.
26. The electronic equipment of claim 24, wherein a radio frequency power amplifier is
disposed between the radio frequency chain and the corresponding sub-array, and the
power distribution factor is used to set a power allocation of the radio frequency
power amplifier.
27. The electronic equipment of claim 10, wherein in the communication with the first
communication apparatus, the second communication apparatus performs reception by
means of an initial set of reception configuration parameters or a particular set
of reception configuration parameters, wherein the reception configuration parameters
of the second communication apparatus are parameters related to directivity when an
antenna at the receiver receives a signal.
28. The electronic equipment of claim 27, wherein the particular set of reception configuration
parameters of the second communication apparatus is a set of reception configuration
parameters in a plurality of sets of reception configuration parameters of the receiver
that optimizes the communication channel quality with the transmitter.
29. The electronic equipment of claim 27, wherein the particular set of reception configuration
parameters of the second communication apparatus is determined in the following manner:
in a case of the first communication apparatus employing each of a plurality of sets
of communication configuration parameters to configure the communication from the
first communication apparatus to the second communication apparatus, and the second
communication apparatus employing each of a plurality of sets of reception configuration
parameters to sequentially receive the communication, a set of reception configuration
parameters that optimizes the communication channel quality is selected as the particular
set of reception configuration parameters.
30. The electronic equipment of claim 29, wherein in each of the first communication and
the second communication, a number of radio frequency chains communicate in parallel
via sub-arrays by using mutually orthogonal training sequences.
31. A method for a first communication apparatus of a wireless communication system, the
first communication apparatus comprising:
a number of antenna sub-arrays, each sub-array being a planar antenna array, each
column or row in the sub-array corresponding to one input terminal;
a plurality of sets of first direction phase shifters, wherein the first direction
phase shifters in each set are disposed between input terminals of the corresponding
sub-arrays and a radio frequency chain,
the method comprises adjusting a first direction angle of an antenna beam for transmitting
a corresponding radio frequency chain signal in a first direction in accordance with
a first control signal.
32. A method for a first communication apparatus of a wireless communication system, wherein
the first communication apparatus is equipped with a number of atenna sub-arrays and
a number of radio frequency chains, the method includes
for each of at least one radio frequency chain of the number of radio frequency chains,
performing a first communication with a second communication apparatus in the wireless
communication system via a first one of the number of antenna sub-arrays corresponding
to the radio frequency chain, so that a first communication configuration parameter
is determined; and
performing a second communication with the second communication apparatus via at least
one of remaining sub-arrays of the number of sub-arrays other than the corresponding
first sub-array, so that a second communication configuration parameter is determined,
wherein a communication configuration parameter for the radio frequency chain is determined
based on the first communication configuration parameter and the second communication
configuration parameter.
33. An electronic equipment for a second communication apparatus of a wireless communication
system, the electronic equipment includes
a processing circuitry configured to: for a corresponding radio frequency chain of
a first communication apparatus in the wireless communication system,
acquire a channel state information in a first communication performed by the first
communication apparatus with respect to the second communication apparatus via a first
one of a plurality of antenna sub-arrays of the first communication apparatus corresponding
to the radio frequency chain, so that a first communication configuration parameter
is determined is based on the channel state information; and
acquire a channel state information in a second communication performed by the first
communication apparatus with respect to the second communication apparatus via at
least one of remaining antenna sub-arrays of the plurality of antenna sub-arrays of
the first communication apparatus other than the corresponding first antenna sub-array,
so that a second communication configuration parameter is determined is based on the
channel state information,
wherein a communication configuration parameter for the radio frequency chain is determined
based on the first communication configuration parameter and the second communication
configuration parameter.
34. A method for a second communication apparatus of a wireless communication system,
comprising:
for a corresponding radio frequency chain of a first communication apparatus in the
wireless communication system,
acquiring a channel state information in a first communication performed by the first
communication apparatus with respect to the second communication apparatus via a first
one of a plurality of antenna sub-arrays of the first communication apparatus corresponding
to the radio frequency chain, so that a first communication configuration parameter
is determined is based on the channel state information; and
acquiring a channel state information in a second communication performed by the first
communication apparatus with respect to the second communication apparatus via at
least one of remaining antenna sub-arrays of the plurality of antenna sub-arrays of
the first communication apparatus other than the corresponding first antenna sub-array,
so that a second communication configuration parameter is determined is based on the
channel state information,
wherein a communication configuration parameter for the radio frequency chain is determined
based on the first communication configuration parameter and the second communication
configuration parameter.
35. An electronic equipment for a first communication apparatus of a wireless communication
system, comprising:
a number of antenna sub-arrays, each sub-array comprising a plurality of antennas,
each antenna being connected to at least one phase shifter; and
a plurality of additional phase shifters, each additional phase shifter being disposed
between one sub-array and one radio frequency chain, such that one radio frequency
chain is connected to a plurality of antenna sub-arrays through a plurality of additional
phase shifters, respectively.
36. A device, comprising:
one or more processors, and
one or more storage devices, comprising instructions, which, when executed by the
one or more processors, causes performance of the method of any of Claims 31, 32 or
34.
37. An apparatus comprising means for performing the method of any of Claims 31, 32 or
34.
38. A storage medium storing instructions thereon, which, when executed by a processor,
causes performance of the method of any of Claims 31, 32 or 34.